[RFC PATCH 02/16] x86/xen: cpuid support in xenhost_t

[Ankur Arora]

xen_cpuid_base() is used to probe and setup features early in a
guest's lifetime.

We want this to behave differently depending on xenhost->type: for
instance, local xenhosts cannot intercept the cpuid instruction at all.

Add op (*cpuid_base)() in xenhost_ops_t.

Signed-off-by: Ankur Arora <ankur.a.arora@xxxxxxxxxx>
---
 arch/x86/include/asm/xen/hypervisor.h |  2 +-
 arch/x86/pci/xen.c                    |  2 +-
 arch/x86/xen/enlighten_hvm.c          |  7 +++++--
 arch/x86/xen/enlighten_pv.c           | 16 +++++++++++++++-
 arch/x86/xen/enlighten_pvh.c          |  4 ++++
 drivers/tty/hvc/hvc_xen.c             |  2 +-
 drivers/xen/grant-table.c             |  3 ++-
 drivers/xen/xenbus/xenbus_xs.c        |  3 ++-
 include/xen/xenhost.h                 | 21 +++++++++++++++++++++
 9 files changed, 52 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/xen/hypervisor.h b/arch/x86/include/asm/xen/hypervisor.h
index 39171b3646bb..6c4cdcdf997d 100644
--- a/arch/x86/include/asm/xen/hypervisor.h
+++ b/arch/x86/include/asm/xen/hypervisor.h
@@ -53,7 +53,7 @@ static inline bool xen_x2apic_para_available(void)
 #else
 static inline bool xen_x2apic_para_available(void)
 {
-	return (xen_cpuid_base() != 0);
+	return (xen_cpuid_base(NULL) != 0);
 }
 #endif
 
diff --git a/arch/x86/pci/xen.c b/arch/x86/pci/xen.c
index 9112d1cb397b..d1a3b9f08289 100644
--- a/arch/x86/pci/xen.c
+++ b/arch/x86/pci/xen.c
@@ -431,7 +431,7 @@ void __init xen_msi_init(void)
 		 * event channels for MSI handling and instead use regular
 		 * APIC processing
 		 */
-		uint32_t eax = cpuid_eax(xen_cpuid_base() + 4);
+		uint32_t eax = cpuid_eax(xenhost_cpuid_base(xh_default) + 4);
 
 		if (((eax & XEN_HVM_CPUID_X2APIC_VIRT) && x2apic_mode) ||
 		    ((eax & XEN_HVM_CPUID_APIC_ACCESS_VIRT) && boot_cpu_has(X86_FEATURE_APIC)))
diff --git a/arch/x86/xen/enlighten_hvm.c b/arch/x86/xen/enlighten_hvm.c
index 100452f4f44c..ffc5791675b2 100644
--- a/arch/x86/xen/enlighten_hvm.c
+++ b/arch/x86/xen/enlighten_hvm.c
@@ -83,7 +83,10 @@ static void __init xen_hvm_init_mem_mapping(void)
 	xen_vcpu_info_reset(0);
 }
 
+extern uint32_t xen_pv_cpuid_base(xenhost_t *xh);
+
 xenhost_ops_t xh_hvm_ops = {
+	.cpuid_base = xen_pv_cpuid_base,
 };
 
 xenhost_ops_t xh_hvm_nested_ops = {
@@ -94,7 +97,7 @@ static void __init init_hvm_pv_info(void)
 	int major, minor;
 	uint32_t eax, ebx, ecx, edx, base;
 
-	base = xen_cpuid_base();
+	base = xenhost_cpuid_base(xh_default);
 	eax = cpuid_eax(base + 1);
 
 	major = eax >> 16;
@@ -250,7 +253,7 @@ static uint32_t __init xen_platform_hvm(void)
 	if (xen_pv_domain() || xen_nopv)
 		return 0;
 
-	return xen_cpuid_base();
+	return xenhost_cpuid_base(xh_default);
 }
 
 static __init void xen_hvm_guest_late_init(void)
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index bb6e811c1525..a4e04b0cc596 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -1189,10 +1189,23 @@ static void __init xen_dom0_set_legacy_features(void)
 	x86_platform.legacy.rtc = 1;
 }
 
+uint32_t xen_pv_cpuid_base(xenhost_t *xh)
+{
+	return hypervisor_cpuid_base("XenVMMXenVMM", 2);
+}
+
+uint32_t xen_pv_nested_cpuid_base(xenhost_t *xh)
+{
+	return hypervisor_cpuid_base("XenVMMXenVMM",
+				2 /* nested specific leaf? */);
+}
+
 xenhost_ops_t xh_pv_ops = {
+	.cpuid_base = xen_pv_cpuid_base,
 };
 
 xenhost_ops_t xh_pv_nested_ops = {
+	.cpuid_base = xen_pv_nested_cpuid_base,
 };
 
 /* First C function to be called on Xen boot */
@@ -1469,7 +1482,8 @@ static int xen_cpu_dead_pv(unsigned int cpu)
 static uint32_t __init xen_platform_pv(void)
 {
 	if (xen_pv_domain())
-		return xen_cpuid_base();
+		/* xenhost is setup in xen_start_kernel. */
+		return xenhost_cpuid_base(xh_default);
 
 	return 0;
 }
diff --git a/arch/x86/xen/enlighten_pvh.c b/arch/x86/xen/enlighten_pvh.c
index 826c296d27a3..c07eba169572 100644
--- a/arch/x86/xen/enlighten_pvh.c
+++ b/arch/x86/xen/enlighten_pvh.c
@@ -29,6 +29,10 @@ void __init xen_pvh_init(void)
 	u32 msr;
 	u64 pfn;
 
+	/*
+	 * Note: we have already called xen_cpuid_base() in
+	 * hypervisor_specific_init()
+	 */
 	xenhost_register(xenhost_r1, &xh_hvm_ops);
 
 	/*
diff --git a/drivers/tty/hvc/hvc_xen.c b/drivers/tty/hvc/hvc_xen.c
index dc43fa96c3de..5e5ca35d7187 100644
--- a/drivers/tty/hvc/hvc_xen.c
+++ b/drivers/tty/hvc/hvc_xen.c
@@ -595,7 +595,7 @@ console_initcall(xen_cons_init);
 #ifdef CONFIG_X86
 static void xen_hvm_early_write(uint32_t vtermno, const char *str, int len)
 {
-	if (xen_cpuid_base())
+	if (xen_cpuid_base(xh_default))
 		outsb(0xe9, str, len);
 }
 #else
diff --git a/drivers/xen/grant-table.c b/drivers/xen/grant-table.c
index 7ea6fb6a2e5d..98af259d0d4f 100644
--- a/drivers/xen/grant-table.c
+++ b/drivers/xen/grant-table.c
@@ -50,6 +50,7 @@
 #endif
 
 #include <xen/xen.h>
+#include <xen/xenhost.h>
 #include <xen/interface/xen.h>
 #include <xen/page.h>
 #include <xen/grant_table.h>
@@ -1318,7 +1319,7 @@ static bool gnttab_need_v2(void)
 	uint32_t base, width;
 
 	if (xen_pv_domain()) {
-		base = xen_cpuid_base();
+		base = xenhost_cpuid_base(xh_default);
 		if (cpuid_eax(base) < 5)
 			return false;	/* Information not available, use V1. */
 		width = cpuid_ebx(base + 5) &
diff --git a/drivers/xen/xenbus/xenbus_xs.c b/drivers/xen/xenbus/xenbus_xs.c
index 49a3874ae6bb..3236d1b1fa01 100644
--- a/drivers/xen/xenbus/xenbus_xs.c
+++ b/drivers/xen/xenbus/xenbus_xs.c
@@ -49,6 +49,7 @@
 #include <asm/xen/hypervisor.h>
 #include <xen/xenbus.h>
 #include <xen/xen.h>
+#include <xen/xenhost.h>
 #include "xenbus.h"
 
 /*
@@ -722,7 +723,7 @@ static bool xen_strict_xenbus_quirk(void)
 #ifdef CONFIG_X86
 	uint32_t eax, ebx, ecx, edx, base;
 
-	base = xen_cpuid_base();
+	base = xenhost_cpuid_base(xh_default);
 	cpuid(base + 1, &eax, &ebx, &ecx, &edx);
 
 	if ((eax >> 16) < 4)
diff --git a/include/xen/xenhost.h b/include/xen/xenhost.h
index a58e883f144e..13a70bdadfd2 100644
--- a/include/xen/xenhost.h
+++ b/include/xen/xenhost.h
@@ -1,6 +1,9 @@
 #ifndef __XENHOST_H
 #define __XENHOST_H
 
+#include <xen/interface/features.h>
+#include <xen/interface/xen.h>
+#include <asm/xen/hypervisor.h>
 /*
  * Xenhost abstracts out the Xen interface. It co-exists with the PV/HVM/PVH
  * abstractions (x86_init, hypervisor_x86, pv_ops etc) and is meant to
@@ -70,6 +73,16 @@ typedef struct {
 } xenhost_t;
 
 typedef struct xenhost_ops {
+	/*
+	 * xen_cpuid is used to probe features early.
+	 * xenhost_r0:
+	 *   Implementation could not use cpuid at all: it's difficult to
+	 *   intercept cpuid instruction locally.
+	 * xenhost_r1:
+	 * xenhost_r2:
+	 *   Separate cpuid-leafs?
+	 */
+	uint32_t (*cpuid_base)(xenhost_t *xenhost);
 } xenhost_ops_t;
 
 extern xenhost_t *xh_default, *xh_remote;
@@ -92,4 +105,12 @@ void __xenhost_unregister(enum xenhost_type type);
 	for ((xh) = (xenhost_t **) &xenhosts[0];	\
 		(((xh) - (xenhost_t **)&xenhosts) < 2) && (*xh)->type != xenhost_invalid; (xh)++)
 
+static inline uint32_t xenhost_cpuid_base(xenhost_t *xh)
+{
+	if (xh)
+		return (xh->ops->cpuid_base)(xh);
+	else
+		return xen_cpuid_base();
+}
+
 #endif /* __XENHOST_H */
-- 
2.20.1