From b9b4fe3a72b60c8d74a9ffb61aa778f04eaddd87 Mon Sep 17 00:00:00 2001 From: Dexuan Cui Date: Thu, 24 Aug 2023 01:07:10 -0700 Subject: [PATCH] x86/hyperv: Use TDX GHCI to access some MSRs in a TDX VM with the paravisor When the paravisor is present, a SNP VM must use GHCB to access some special MSRs, including HV_X64_MSR_GUEST_OS_ID and some SynIC MSRs. Similarly, when the paravisor is present, a TDX VM must use TDX GHCI to access the same MSRs. Implement hv_tdx_msr_write() and hv_tdx_msr_read(), and use the helper functions hv_ivm_msr_read() and hv_ivm_msr_write() to access the MSRs in a unified way for SNP/TDX VMs with the paravisor. Do not export hv_tdx_msr_write() and hv_tdx_msr_read(), because we never really used hv_ghcb_msr_write() and hv_ghcb_msr_read() in any module. Update arch/x86/include/asm/mshyperv.h so that the kernel can still build if CONFIG_AMD_MEM_ENCRYPT or CONFIG_INTEL_TDX_GUEST is not set, or neither is set. Signed-off-by: Dexuan Cui Reviewed-by: Tianyu Lan Reviewed-by: Michael Kelley Signed-off-by: Wei Liu Link: https://lore.kernel.org/r/20230824080712.30327-9-decui@microsoft.com --- arch/x86/hyperv/hv_init.c | 8 ++-- arch/x86/hyperv/ivm.c | 69 +++++++++++++++++++++++++++++++-- arch/x86/include/asm/mshyperv.h | 8 ++-- arch/x86/kernel/cpu/mshyperv.c | 8 ++-- 4 files changed, 77 insertions(+), 16 deletions(-) diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c index 3729eee21e47..c4cffa3b1c3c 100644 --- a/arch/x86/hyperv/hv_init.c +++ b/arch/x86/hyperv/hv_init.c @@ -500,8 +500,8 @@ void __init hyperv_init(void) guest_id = hv_generate_guest_id(LINUX_VERSION_CODE); wrmsrl(HV_X64_MSR_GUEST_OS_ID, guest_id); - /* Hyper-V requires to write guest os id via ghcb in SNP IVM. */ - hv_ghcb_msr_write(HV_X64_MSR_GUEST_OS_ID, guest_id); + /* With the paravisor, the VM must also write the ID via GHCB/GHCI */ + hv_ivm_msr_write(HV_X64_MSR_GUEST_OS_ID, guest_id); /* A TDX VM with no paravisor only uses TDX GHCI rather than hv_hypercall_pg */ if (hv_isolation_type_tdx() && !ms_hyperv.paravisor_present) @@ -590,7 +590,7 @@ skip_hypercall_pg_init: clean_guest_os_id: wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0); - hv_ghcb_msr_write(HV_X64_MSR_GUEST_OS_ID, 0); + hv_ivm_msr_write(HV_X64_MSR_GUEST_OS_ID, 0); cpuhp_remove_state(cpuhp); free_ghcb_page: free_percpu(hv_ghcb_pg); @@ -611,7 +611,7 @@ void hyperv_cleanup(void) /* Reset our OS id */ wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0); - hv_ghcb_msr_write(HV_X64_MSR_GUEST_OS_ID, 0); + hv_ivm_msr_write(HV_X64_MSR_GUEST_OS_ID, 0); /* * Reset hypercall page reference before reset the page, diff --git a/arch/x86/hyperv/ivm.c b/arch/x86/hyperv/ivm.c index 7bd0359d5e38..fbc07493fcb4 100644 --- a/arch/x86/hyperv/ivm.c +++ b/arch/x86/hyperv/ivm.c @@ -24,6 +24,7 @@ #include #include #include +#include #ifdef CONFIG_AMD_MEM_ENCRYPT @@ -186,7 +187,7 @@ bool hv_ghcb_negotiate_protocol(void) return true; } -void hv_ghcb_msr_write(u64 msr, u64 value) +static void hv_ghcb_msr_write(u64 msr, u64 value) { union hv_ghcb *hv_ghcb; void **ghcb_base; @@ -214,9 +215,8 @@ void hv_ghcb_msr_write(u64 msr, u64 value) local_irq_restore(flags); } -EXPORT_SYMBOL_GPL(hv_ghcb_msr_write); -void hv_ghcb_msr_read(u64 msr, u64 *value) +static void hv_ghcb_msr_read(u64 msr, u64 *value) { union hv_ghcb *hv_ghcb; void **ghcb_base; @@ -246,10 +246,71 @@ void hv_ghcb_msr_read(u64 msr, u64 *value) | ((u64)lower_32_bits(hv_ghcb->ghcb.save.rdx) << 32); local_irq_restore(flags); } -EXPORT_SYMBOL_GPL(hv_ghcb_msr_read); +#else +static inline void hv_ghcb_msr_write(u64 msr, u64 value) {} +static inline void hv_ghcb_msr_read(u64 msr, u64 *value) {} #endif /* CONFIG_AMD_MEM_ENCRYPT */ +#ifdef CONFIG_INTEL_TDX_GUEST +static void hv_tdx_msr_write(u64 msr, u64 val) +{ + struct tdx_hypercall_args args = { + .r10 = TDX_HYPERCALL_STANDARD, + .r11 = EXIT_REASON_MSR_WRITE, + .r12 = msr, + .r13 = val, + }; + + u64 ret = __tdx_hypercall(&args); + + WARN_ONCE(ret, "Failed to emulate MSR write: %lld\n", ret); +} + +static void hv_tdx_msr_read(u64 msr, u64 *val) +{ + struct tdx_hypercall_args args = { + .r10 = TDX_HYPERCALL_STANDARD, + .r11 = EXIT_REASON_MSR_READ, + .r12 = msr, + }; + + u64 ret = __tdx_hypercall_ret(&args); + + if (WARN_ONCE(ret, "Failed to emulate MSR read: %lld\n", ret)) + *val = 0; + else + *val = args.r11; +} +#else +static inline void hv_tdx_msr_write(u64 msr, u64 value) {} +static inline void hv_tdx_msr_read(u64 msr, u64 *value) {} +#endif /* CONFIG_INTEL_TDX_GUEST */ + +#if defined(CONFIG_AMD_MEM_ENCRYPT) || defined(CONFIG_INTEL_TDX_GUEST) +void hv_ivm_msr_write(u64 msr, u64 value) +{ + if (!ms_hyperv.paravisor_present) + return; + + if (hv_isolation_type_tdx()) + hv_tdx_msr_write(msr, value); + else if (hv_isolation_type_snp()) + hv_ghcb_msr_write(msr, value); +} + +void hv_ivm_msr_read(u64 msr, u64 *value) +{ + if (!ms_hyperv.paravisor_present) + return; + + if (hv_isolation_type_tdx()) + hv_tdx_msr_read(msr, value); + else if (hv_isolation_type_snp()) + hv_ghcb_msr_read(msr, value); +} +#endif + #if defined(CONFIG_AMD_MEM_ENCRYPT) || defined(CONFIG_INTEL_TDX_GUEST) /* * hv_mark_gpa_visibility - Set pages visible to host via hvcall. diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h index a9f453c39371..101f71b85cfd 100644 --- a/arch/x86/include/asm/mshyperv.h +++ b/arch/x86/include/asm/mshyperv.h @@ -275,14 +275,10 @@ int hv_map_ioapic_interrupt(int ioapic_id, bool level, int vcpu, int vector, int hv_unmap_ioapic_interrupt(int ioapic_id, struct hv_interrupt_entry *entry); #ifdef CONFIG_AMD_MEM_ENCRYPT -void hv_ghcb_msr_write(u64 msr, u64 value); -void hv_ghcb_msr_read(u64 msr, u64 *value); bool hv_ghcb_negotiate_protocol(void); void __noreturn hv_ghcb_terminate(unsigned int set, unsigned int reason); int hv_snp_boot_ap(int cpu, unsigned long start_ip); #else -static inline void hv_ghcb_msr_write(u64 msr, u64 value) {} -static inline void hv_ghcb_msr_read(u64 msr, u64 *value) {} static inline bool hv_ghcb_negotiate_protocol(void) { return false; } static inline void hv_ghcb_terminate(unsigned int set, unsigned int reason) {} static inline int hv_snp_boot_ap(int cpu, unsigned long start_ip) { return 0; } @@ -292,8 +288,12 @@ extern bool hv_isolation_type_snp(void); #if defined(CONFIG_AMD_MEM_ENCRYPT) || defined(CONFIG_INTEL_TDX_GUEST) void hv_vtom_init(void); +void hv_ivm_msr_write(u64 msr, u64 value); +void hv_ivm_msr_read(u64 msr, u64 *value); #else static inline void hv_vtom_init(void) {} +static inline void hv_ivm_msr_write(u64 msr, u64 value) {} +static inline void hv_ivm_msr_read(u64 msr, u64 *value) {} #endif static inline bool hv_is_synic_reg(unsigned int reg) diff --git a/arch/x86/kernel/cpu/mshyperv.c b/arch/x86/kernel/cpu/mshyperv.c index 4c5a174935ca..4f51dac9eeb2 100644 --- a/arch/x86/kernel/cpu/mshyperv.c +++ b/arch/x86/kernel/cpu/mshyperv.c @@ -70,8 +70,8 @@ u64 hv_get_non_nested_register(unsigned int reg) { u64 value; - if (hv_is_synic_reg(reg) && hv_isolation_type_snp()) - hv_ghcb_msr_read(reg, &value); + if (hv_is_synic_reg(reg) && ms_hyperv.paravisor_present) + hv_ivm_msr_read(reg, &value); else rdmsrl(reg, value); return value; @@ -80,8 +80,8 @@ EXPORT_SYMBOL_GPL(hv_get_non_nested_register); void hv_set_non_nested_register(unsigned int reg, u64 value) { - if (hv_is_synic_reg(reg) && hv_isolation_type_snp()) { - hv_ghcb_msr_write(reg, value); + if (hv_is_synic_reg(reg) && ms_hyperv.paravisor_present) { + hv_ivm_msr_write(reg, value); /* Write proxy bit via wrmsl instruction */ if (hv_is_sint_reg(reg)) -- 2.25.1