Messages in this thread Patch in this message | | | From | Kuppuswamy Sathyanarayanan <> | Subject | [PATCH v7 10/12] x86/tdx: Add MSR support for TDX guest | Date | Thu, 16 Sep 2021 11:35:48 -0700 |
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From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Operations on context-switched MSRs can be run natively. The rest of MSRs should be handled through TDVMCALLs.
TDVMCALL[Instruction.RDMSR] and TDVMCALL[Instruction.WRMSR] provide MSR oprations.
RDMSR and WRMSR specification details can be found in Guest-Host-Communication Interface (GHCI) for Intel Trust Domain Extensions (Intel TDX) specification, sec 3.10, 3.11.
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reviewed-by: Andi Kleen <ak@linux.intel.com> Reviewed-by: Tony Luck <tony.luck@intel.com> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com> ---
Changes since v6: * None
Changes since v5: * Renamed "tdg" prefix with "tdx". * Added comments for _tdx_hypercall() usage in MSR read/write functions.
Change since v4: * Removed You usage from commit log.
Changes since v3: * None
arch/x86/kernel/tdx.c | 77 +++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 75 insertions(+), 2 deletions(-)
diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c index ec1008cc42d9..5c52dde4a5fd 100644 --- a/arch/x86/kernel/tdx.c +++ b/arch/x86/kernel/tdx.c @@ -91,6 +91,65 @@ static __cpuidle void tdx_safe_halt(void) _tdx_halt(irq_disabled, do_sti); } +static bool tdx_is_context_switched_msr(unsigned int msr) +{ + switch (msr) { + case MSR_EFER: + case MSR_IA32_CR_PAT: + case MSR_FS_BASE: + case MSR_GS_BASE: + case MSR_KERNEL_GS_BASE: + case MSR_IA32_SYSENTER_CS: + case MSR_IA32_SYSENTER_EIP: + case MSR_IA32_SYSENTER_ESP: + case MSR_STAR: + case MSR_LSTAR: + case MSR_SYSCALL_MASK: + case MSR_IA32_XSS: + case MSR_TSC_AUX: + case MSR_IA32_BNDCFGS: + return true; + } + return false; +} + +static u64 tdx_read_msr_safe(unsigned int msr, int *err) +{ + struct tdx_hypercall_output out = {0}; + u64 ret; + + WARN_ON_ONCE(tdx_is_context_switched_msr(msr)); + + /* + * Emulate the MSR read via hypercall. More info about ABI + * can be found in TDX Guest-Host-Communication Interface + * (GHCI), sec 3.10. + */ + ret = _tdx_hypercall(EXIT_REASON_MSR_READ, msr, 0, 0, 0, &out); + + *err = ret ? -EIO : 0; + + return out.r11; +} + +static int tdx_write_msr_safe(unsigned int msr, unsigned int low, + unsigned int high) +{ + u64 ret; + + WARN_ON_ONCE(tdx_is_context_switched_msr(msr)); + + /* + * Emulate the MSR write via hypercall. More info about ABI + * can be found in TDX Guest-Host-Communication Interface + * (GHCI) sec 3.11. + */ + ret = _tdx_hypercall(EXIT_REASON_MSR_WRITE, msr, (u64)high << 32 | low, + 0, 0, NULL); + + return ret ? -EIO : 0; +} + unsigned long tdx_get_ve_info(struct ve_info *ve) { struct tdx_module_output out = {0}; @@ -117,19 +176,33 @@ unsigned long tdx_get_ve_info(struct ve_info *ve) int tdx_handle_virtualization_exception(struct pt_regs *regs, struct ve_info *ve) { + unsigned long val; + int ret = 0; + switch (ve->exit_reason) { case EXIT_REASON_HLT: tdx_halt(); break; + case EXIT_REASON_MSR_READ: + val = tdx_read_msr_safe(regs->cx, (unsigned int *)&ret); + if (!ret) { + regs->ax = (u32)val; + regs->dx = val >> 32; + } + break; + case EXIT_REASON_MSR_WRITE: + ret = tdx_write_msr_safe(regs->cx, regs->ax, regs->dx); + break; default: pr_warn("Unexpected #VE: %lld\n", ve->exit_reason); return -EFAULT; } /* After successful #VE handling, move the IP */ - regs->ip += ve->instr_len; + if (!ret) + regs->ip += ve->instr_len; - return 0; + return ret; } void __init tdx_early_init(void) -- 2.25.1
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