Messages in this thread Patch in this message | | | From | Kuppuswamy Sathyanarayanan <> | Subject | [PATCH v6 05/10] x86/tdx: Handle port I/O | Date | Wed, 22 Sep 2021 15:52:34 -0700 |
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From: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
TDX hypervisors cannot emulate instructions directly. This includes port IO which is normally emulated in the hypervisor. All port IO instructions inside TDX trigger the #VE exception in the guest and would be normally emulated there.
Also string I/O is not supported in TDX guest. So, unroll the string I/O operation into a loop operating on one element at a time. This method is similar to AMD SEV, so just extend the support for TDX guest platform.
Add a new confidential guest flag CC_ATTR_GUEST_UNROLL_STRING_IO to add string unroll support in asm/io.h
Co-developed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com> Signed-off-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Reviewed-by: Andi Kleen <ak@linux.intel.com> Reviewed-by: Dan Williams <dan.j.williams@intel.com> ---
Changes since v5: * Changed prot_guest_has() to cc_platform_has().
Changes since v4: * Changed order of variable declaration in tdx_handle_io(). * Changed tdg_* prefix with tdx_*.
Changes since v3: * Included PATTR_GUEST_UNROLL_STRING_IO protected guest flag addition change in this patch. * Rebased on top of Tom Lendacks protected guest change.
Changes since v2: * None
Changes since v1: * Fixed comments for tdg_handle_io(). * Used _tdx_hypercall() instead of __tdx_hypercall() in tdg_handle_io().
arch/x86/include/asm/io.h | 7 +++++-- arch/x86/kernel/cpu/intel.c | 1 + arch/x86/kernel/tdx.c | 35 +++++++++++++++++++++++++++++++++++ include/linux/cc_platform.h | 11 +++++++++++ 4 files changed, 52 insertions(+), 2 deletions(-)
diff --git a/arch/x86/include/asm/io.h b/arch/x86/include/asm/io.h index fa6aa43e5dc3..67e0c4a0a0f4 100644 --- a/arch/x86/include/asm/io.h +++ b/arch/x86/include/asm/io.h @@ -40,6 +40,7 @@ #include <linux/string.h> #include <linux/compiler.h> +#include <linux/cc_platform.h> #include <asm/page.h> #include <asm/tdx.h> #include <asm/early_ioremap.h> @@ -310,7 +311,8 @@ static inline unsigned type in##bwl##_p(int port) \ \ static inline void outs##bwl(int port, const void *addr, unsigned long count) \ { \ - if (sev_key_active()) { \ + if (sev_key_active() || \ + cc_platform_has(CC_ATTR_GUEST_UNROLL_STRING_IO)) { \ unsigned type *value = (unsigned type *)addr; \ while (count) { \ out##bwl(*value, port); \ @@ -326,7 +328,8 @@ static inline void outs##bwl(int port, const void *addr, unsigned long count) \ \ static inline void ins##bwl(int port, void *addr, unsigned long count) \ { \ - if (sev_key_active()) { \ + if (sev_key_active() || \ + cc_platform_has(CC_ATTR_GUEST_UNROLL_STRING_IO)) { \ unsigned type *value = (unsigned type *)addr; \ while (count) { \ *value = in##bwl(port); \ diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index ab337c194beb..c7c02c2e7601 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -66,6 +66,7 @@ bool intel_cc_platform_has(enum cc_attr attr) { switch (attr) { case CC_ATTR_GUEST_TDX: + case CC_ATTR_GUEST_UNROLL_STRING_IO: return cpu_feature_enabled(X86_FEATURE_TDX_GUEST); default: return false; diff --git a/arch/x86/kernel/tdx.c b/arch/x86/kernel/tdx.c index b3515f789f64..31a2c2a9722a 100644 --- a/arch/x86/kernel/tdx.c +++ b/arch/x86/kernel/tdx.c @@ -180,6 +180,38 @@ static u64 tdx_handle_cpuid(struct pt_regs *regs) return ret; } +/* + * tdx_handle_early_io() cannot be re-used in #VE handler for handling + * I/O because the way of handling string I/O is different between + * normal and early I/O case. Also, once trace support is enabled, + * tdx_handle_io() will be extended to use trace calls which is also + * not valid for early I/O cases. + */ +static void tdx_handle_io(struct pt_regs *regs, u32 exit_qual) +{ + struct tdx_hypercall_output outh; + int out, size, port, ret; + bool string; + u64 mask; + + string = VE_IS_IO_STRING(exit_qual); + + /* I/O strings ops are unrolled at build time. */ + BUG_ON(string); + + out = VE_IS_IO_OUT(exit_qual); + size = VE_GET_IO_SIZE(exit_qual); + port = VE_GET_PORT_NUM(exit_qual); + mask = GENMASK(8 * size, 0); + + ret = _tdx_hypercall(EXIT_REASON_IO_INSTRUCTION, size, out, port, + regs->ax, &outh); + if (!out) { + regs->ax &= ~mask; + regs->ax |= (ret ? UINT_MAX : outh.r11) & mask; + } +} + unsigned long tdx_get_ve_info(struct ve_info *ve) { struct tdx_module_output out = {0}; @@ -226,6 +258,9 @@ int tdx_handle_virtualization_exception(struct pt_regs *regs, case EXIT_REASON_CPUID: ret = tdx_handle_cpuid(regs); break; + case EXIT_REASON_IO_INSTRUCTION: + tdx_handle_io(regs, ve->exit_qual); + break; default: pr_warn("Unexpected #VE: %lld\n", ve->exit_reason); return -EFAULT; diff --git a/include/linux/cc_platform.h b/include/linux/cc_platform.h index e38430e6e396..253fd4ca7178 100644 --- a/include/linux/cc_platform.h +++ b/include/linux/cc_platform.h @@ -70,6 +70,17 @@ enum cc_attr { * Examples include SEV-ES. */ CC_ATTR_GUEST_TDX, + + /** + * @CC_ATTR_GUEST_UNROLL_STRING_IO: String I/O is implemented with + * IN/OUT instructions + * + * The platform/OS is running as a guest/virtual machine and uses + * IN/OUT instructions in place of string I/O. + * + * Examples include TDX Guest. + */ + CC_ATTR_GUEST_UNROLL_STRING_IO, }; #ifdef CONFIG_ARCH_HAS_CC_PLATFORM -- 2.25.1
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