linux-kernel - [PATCH 07/12] KVM: SVM: Adding support for configuring x2APIC MSRs interception

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Date:   Tue, 5 Apr 2022 18:08:50 -0500
From:   Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To:     <linux-kernel@...r.kernel.org>, <kvm@...r.kernel.org>,
        <x86@...nel.org>
CC:     <mlevitsk@...hat.com>, <seanjc@...gle.com>, <pbonzini@...hat.com>,
        <joro@...tes.org>, <tglx@...utronix.de>, <mingo@...hat.com>,
        <bp@...en8.de>, <peterz@...radead.org>, <hpa@...or.com>,
        <jon.grimm@....com>, <wei.huang2@....com>, <terry.bowman@....com>,
        Suravee Suthikulpanit <suravee.suthikulpanit@....com>
Subject: [PATCH 07/12] KVM: SVM: Adding support for configuring x2APIC MSRs interception

When enabling x2APIC virtualization (x2AVIC), the interception of
x2APIC MSRs must be disabled to let the hardware virtualize guest
MSR accesses.

Current implementation keeps track of list of MSR interception state
in the svm_direct_access_msrs array. Therefore, extends the array to
include x2APIC MSRs.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@....com>
---
 arch/x86/kvm/svm/svm.c | 30 +++++++++++++++++++++++++++++-
 arch/x86/kvm/svm/svm.h |  5 +++--
 2 files changed, 32 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index bbdc16c4b6d7..56ad9ba05111 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -89,7 +89,7 @@ static uint64_t osvw_len = 4, osvw_status;
 static DEFINE_PER_CPU(u64, current_tsc_ratio);
 #define TSC_RATIO_DEFAULT	0x0100000000ULL
 
-static const struct svm_direct_access_msrs {
+static struct svm_direct_access_msrs {
 	u32 index;   /* Index of the MSR */
 	bool always; /* True if intercept is initially cleared */
 } direct_access_msrs[MAX_DIRECT_ACCESS_MSRS] = {
@@ -786,6 +786,33 @@ static void add_msr_offset(u32 offset)
 	BUG();
 }
 
+static void init_direct_access_msrs(void)
+{
+	int i, j;
+
+	/* Find first MSR_INVALID */
+	for (i = 0; i < MAX_DIRECT_ACCESS_MSRS; i++) {
+		if (direct_access_msrs[i].index == MSR_INVALID)
+			break;
+	}
+	BUG_ON(i >= MAX_DIRECT_ACCESS_MSRS);
+
+	/*
+	 * Initialize direct_access_msrs entries to intercept X2APIC MSRs
+	 * (range 0x800 to 0x8ff)
+	 */
+	for (j = 0; j < 0x100; j++) {
+		direct_access_msrs[i + j].index = boot_cpu_has(X86_FEATURE_X2AVIC) ?
+						  (APIC_BASE_MSR + j) : MSR_INVALID;
+		direct_access_msrs[i + j].always = false;
+	}
+	BUG_ON(i + j >= MAX_DIRECT_ACCESS_MSRS);
+
+	/* Initialize last entry */
+	direct_access_msrs[i + j].index = MSR_INVALID;
+	direct_access_msrs[i + j].always = true;
+}
+
 static void init_msrpm_offsets(void)
 {
 	int i;
@@ -4765,6 +4792,7 @@ static __init int svm_hardware_setup(void)
 	memset(iopm_va, 0xff, PAGE_SIZE * (1 << order));
 	iopm_base = page_to_pfn(iopm_pages) << PAGE_SHIFT;
 
+	init_direct_access_msrs();
 	init_msrpm_offsets();
 
 	supported_xcr0 &= ~(XFEATURE_MASK_BNDREGS | XFEATURE_MASK_BNDCSR);
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index b53c83a44ec2..0bbbe8d6a87a 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -27,8 +27,9 @@
 #define	IOPM_SIZE PAGE_SIZE * 3
 #define	MSRPM_SIZE PAGE_SIZE * 2
 
-#define MAX_DIRECT_ACCESS_MSRS	20
-#define MSRPM_OFFSETS	16
+#define MAX_DIRECT_ACCESS_MSRS	(20 + 0x100)
+#define MSRPM_OFFSETS	30
+
 extern u32 msrpm_offsets[MSRPM_OFFSETS] __read_mostly;
 extern bool npt_enabled;
 extern bool intercept_smi;
-- 
2.25.1