Re: [PATCH 3/25][V3] irq_flags / halt routines

["Glauber de Oliveira Costa" <glommer@gmail.com>]

On 8/15/07, Chris Wright <chrisw@sous-sol.org> wrote:
> * Glauber de Oliveira Costa (gcosta@redhat.com) wrote:
> > Only caveat, is that it has to be done before smp gets in the game, and
> > with interrupts disabled. (which makes the function in vsmp.c not eligible).
> >
> > My current option is to force VSMP to use PARAVIRT, as said before, and
> > then fill paravirt_arch_setup, which is currently unused, with code to
> > replace the needed paravirt_ops.fn.
> >
> > I don't know if there is any method to dynamically determine (at this
> > point) that we are in a vsmp arch, and if there are not, it will have to
> > get ifdefs anyway. But at least, they are far more local.
>
> between __cacheline_aligned_in_smp and other compile time bits based on
> VSMP specific INTERNODE_CACHE, etc. I think compile time the way to go.
>
> > I am okay with both, but after all the explanation, I don't think that
> > adding a new pvops is a bad idea. It would make things less cumbersome
> > in this case. Also, hacks like this save_fl may require changes to the
> > hypervisor, right? I don't even know where such hypervisor is, and how
> > easy it is to replace it (it may be deeply hidden in firmware)
>
> No hypervisor change needed.  Just the pv backend needs to return 0 or
> X86_EFLAGS_IF for save_flags (and similar translation on restore_flags).
> Xen uses a simple shared memory flag and does something which you could
> roughly translate into this:
>
>         xen_save_flags()
>         if (xen_vcpu_interrupts_enabled)
>                 return X86_EFLAGS_IF;
>         else
>                 return 0;
>
> This doesn't require any hypervisor changes.  Similarly, VSMP could do
> something along the lines of:
>
>         vsmp_save_flags()
>         flags = native_save_flags();
>         if (flags & X86_EFLAGS_IF) || (flags & X86_EFLAGS_AC)
>                 return X86_EFLAGS_IF;
>         else
>                 return 0;
>

I'm attaching to this message my idea on how would it work.
This is just for comments/considerations. If you all ack this, I'll
spread the changes over the patch series as needed, and then resend
the patches.

-- 
Glauber de Oliveira Costa.
"Free as in Freedom"
http://glommer.net

"The less confident you are, the more serious you have to act."

diff --git a/arch/x86_64/Kconfig b/arch/x86_64/Kconfig
index 00b2fc9..1204b08 100644
--- a/arch/x86_64/Kconfig
+++ b/arch/x86_64/Kconfig
@@ -150,6 +150,7 @@ config X86_PC
 config X86_VSMP
 	bool "Support for ScaleMP vSMP"
 	depends on PCI
+	select PARAVIRT
 	 help
 	  Support for ScaleMP vSMP systems.  Say 'Y' here if this kernel is
 	  supposed to run on these EM64T-based machines.  Only choose this option
diff --git a/arch/x86_64/kernel/paravirt.c b/arch/x86_64/kernel/paravirt.c
index dcd9919..23a8786 100644
--- a/arch/x86_64/kernel/paravirt.c
+++ b/arch/x86_64/kernel/paravirt.c
@@ -22,6 +22,8 @@
 #include <linux/efi.h>
 #include <linux/bcd.h>
 #include <linux/start_kernel.h>
+#include <linux/pci_regs.h>
+#include <linux/pci_ids.h>
 
 #include <asm/bug.h>
 #include <asm/paravirt.h>
@@ -40,15 +42,30 @@
 #include <asm/asm-offsets.h>
 #include <asm/smp.h>
 #include <asm/irqflags.h>
+#include <asm/pci-direct.h>
 
 /* nop stub */
 void _paravirt_nop(void)
 {
 }
 
+int arch_is_vsmp = 0;
+
 /* natively, we do normal setup, but we still need to return something */
 static int native_arch_setup(void)
 {
+	if (!early_pci_allowed())
+		goto out;
+		
+	if ((read_pci_config_16(0, 0x1f, 0, PCI_VENDOR_ID) == PCI_VENDOR_ID_SCALEMP) &&
+            (read_pci_config_16(0, 0x1f, 0, PCI_DEVICE_ID) == PCI_DEVICE_ID_SCALEMP_VSMP_CTL)) {
+		paravirt_ops.irq_disable = vsmp_irq_disable;
+		paravirt_ops.irq_enable  = vsmp_irq_enable;
+		paravirt_ops.save_fl  = vsmp_save_flags;
+		arch_is_vsmp = 1;
+	}
+
+out:
 	return 0;
 }
 
@@ -103,8 +120,6 @@ static unsigned native_patch(u8 type, u16 clobbers, void *insns, unsigned len)
 
 	switch(type) {
 #define SITE(x)	case PARAVIRT_PATCH(x):	start = start_##x; end = end_##x; goto patch_site
-		SITE(irq_disable);
-		SITE(irq_enable);
 		SITE(restore_fl);
 		SITE(save_fl);
 		SITE(iret);
@@ -117,7 +132,23 @@ static unsigned native_patch(u8 type, u16 clobbers, void *insns, unsigned len)
 		SITE(flush_tlb_single);
 		SITE(wbinvd);
 #undef SITE
-
+	case PARAVIRT_PATCH(irq_disable): 
+	case PARAVIRT_PATCH(irq_enable): 
+		start = start_irq_disable;
+		end = end_irq_disable;
+
+		if (type == PARAVIRT_PATCH(irq_enable)) {
+			start = start_irq_enable;
+			end = end_irq_enable;
+		}
+
+		if (arch_is_vsmp) {
+			ret = paravirt_patch_default(type,
+						     clobbers,
+						     insns,
+						     len);
+			break;
+		}
 	patch_site:
 		ret = paravirt_patch_insns(insns, len, start, end);
 		break;
@@ -214,30 +245,6 @@ void init_IRQ(void)
 	paravirt_ops.init_IRQ();
 }
 
-static unsigned long native_save_fl(void)
-{
-	unsigned long f;
-	asm volatile("pushfq ; popq %0":"=g" (f): /* no input */);
-	return f;
-}
-
-static void native_restore_fl(unsigned long f)
-{
-	asm volatile("pushq %0 ; popfq": /* no output */
-			     :"g" (f)
-			     :"memory", "cc");
-}
-
-static void native_irq_disable(void)
-{
-	asm volatile("cli": : :"memory");
-}
-
-static void native_irq_enable(void)
-{
-	asm volatile("sti": : :"memory");
-}
-
 static void native_io_delay(void)
 {
 	asm volatile("outb %al,$0x80");
@@ -328,8 +328,8 @@ struct paravirt_ops paravirt_ops = {
 	.write_cr3 = native_write_cr3,
 	.read_cr4 = native_read_cr4,
 	.write_cr4 = native_write_cr4,
-	.save_fl = native_save_fl,
-	.restore_fl = native_restore_fl,
+	.save_fl = native_save_flags,
+	.restore_fl = native_restore_flags,
 	.irq_disable = native_irq_disable,
 	.irq_enable = native_irq_enable,
 	.safe_halt = native_raw_safe_halt,
diff --git a/arch/x86_64/kernel/vsmp.c b/arch/x86_64/kernel/vsmp.c
index 414caf0..ddfb1b7 100644
--- a/arch/x86_64/kernel/vsmp.c
+++ b/arch/x86_64/kernel/vsmp.c
@@ -15,6 +15,7 @@
 #include <linux/pci_regs.h>
 #include <asm/pci-direct.h>
 #include <asm/io.h>
+#include <asm/irqflags.h>
 
 static int __init vsmp_init(void)
 {
diff --git a/include/asm-x86_64/irqflags.h b/include/asm-x86_64/irqflags.h
index fe0d346..eb993f4 100644
--- a/include/asm-x86_64/irqflags.h
+++ b/include/asm-x86_64/irqflags.h
@@ -16,11 +16,7 @@
  * Interrupt control:
  */
 
-#ifdef CONFIG_PARAVIRT
-#include <asm/paravirt.h>
-#else /* PARAVIRT */
-
-static inline unsigned long __raw_local_save_flags(void)
+static inline unsigned long native_save_flags(void)
 {
 	unsigned long flags;
 
@@ -35,7 +31,7 @@ static inline unsigned long __raw_local_save_flags(void)
 	return flags;
 }
 
-static inline void raw_local_irq_restore(unsigned long flags)
+static inline void native_restore_flags(unsigned long flags)
 {
 	__asm__ __volatile__(
 		"pushq %0 ; popfq"
@@ -45,57 +41,59 @@ static inline void raw_local_irq_restore(unsigned long flags)
 	);
 }
 
-#ifdef CONFIG_X86_VSMP
+static inline void native_irq_disable(void)
+{
+	__asm__ __volatile__("cli" : : : "memory");
+}
+
+static inline void native_irq_enable(void)
+{
+	__asm__ __volatile__("sti" : : : "memory");
+}
+
+static inline long raw_irqs_disabled_flags(unsigned long flags)
+{
+	return !(flags & X86_EFLAGS_IF);
+}
 
 /*
  * Interrupt control for the VSMP architecture:
  */
 
-static inline void raw_local_irq_disable(void)
+static inline unsigned long vsmp_save_flags(void)
 {
-	unsigned long flags = __raw_local_save_flags();
+	unsigned long flags = vsmp_save_flags();
 
-	raw_local_irq_restore((flags & ~X86_EFLAGS_IF) | X86_EFLAGS_AC);
+	if ((flags & X86_EFLAGS_IF) || (flags & X86_EFLAGS_AC))
+		return X86_EFLAGS_IF;
+	return 0;
 }
 
-static inline void raw_local_irq_enable(void)
+static inline void vsmp_irq_disable(void)
 {
 	unsigned long flags = __raw_local_save_flags();
 
-	raw_local_irq_restore((flags | X86_EFLAGS_IF) & (~X86_EFLAGS_AC));
+	raw_local_irq_restore((flags & ~X86_EFLAGS_IF) | X86_EFLAGS_AC);
 }
 
-#else /* CONFIG_X86_VSMP */
-
-static inline void raw_local_irq_disable(void)
+static inline void vsmp_irq_enable(void)
 {
-	__asm__ __volatile__("cli" : : : "memory");
-}
+	unsigned long flags = __raw_local_save_flags();
 
-static inline void raw_local_irq_enable(void)
-{
-	__asm__ __volatile__("sti" : : : "memory");
+	raw_local_irq_restore((flags | X86_EFLAGS_IF) & (~X86_EFLAGS_AC));
 }
 
-#endif /* CONFIG_X86_VSMP */
-#endif /* CONFIG_PARAVIRT */
+#ifdef CONFIG_PARAVIRT
+#include <asm/paravirt.h>
+#else /* PARAVIRT */
+#define __raw_local_save_flags()		native_save_flags()
+#define raw_local_irq_restore(x)		native_restore_flags(x)
+#define raw_local_irq_disable()			native_irq_disable()
+#define raw_local_irq_enable()			native_irq_enable()
+#endif
 
 /* Those are not paravirt stubs, so they live out of the PARAVIRT ifdef */
 
-#ifdef CONFIG_X86_VSMP
-static inline int raw_irqs_disabled_flags(unsigned long flags)
-{
-	return !(flags & X86_EFLAGS_IF) || (flags & X86_EFLAGS_AC);
-}
-
-#else
-static inline int raw_irqs_disabled_flags(unsigned long flags)
-{
-	return !(flags & X86_EFLAGS_IF);
-}
-
-#endif /* CONFIG_X86_VSMP */
-
 #define raw_local_save_flags(flags) \
 		do { (flags) = __raw_local_save_flags(); } while (0)
 /*
diff --git a/include/asm-x86_64/paravirt.h b/include/asm-x86_64/paravirt.h
diff --git a/include/asm-x86_64/processor.h b/include/asm-x86_64/processor.h