Messages in this thread | | | Subject | Re: [RFC PATCH v4 28/28] x86: Add support to make use of Secure Memory Encryption | From | Tom Lendacky <> | Date | Tue, 7 Mar 2017 10:05:00 -0600 |
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On 3/1/2017 12:40 PM, Borislav Petkov wrote: > On Thu, Feb 16, 2017 at 09:48:25AM -0600, Tom Lendacky wrote: >> This patch adds the support to check if SME has been enabled and if >> memory encryption should be activated (checking of command line option >> based on the configuration of the default state). If memory encryption >> is to be activated, then the encryption mask is set and the kernel is >> encrypted "in place." >> >> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> >> --- >> arch/x86/kernel/head_64.S | 1 + >> arch/x86/kernel/mem_encrypt_init.c | 71 +++++++++++++++++++++++++++++++++++- >> arch/x86/mm/mem_encrypt.c | 2 + >> 3 files changed, 73 insertions(+), 1 deletion(-) >> >> diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S >> index edd2f14..e6820e7 100644 >> --- a/arch/x86/kernel/head_64.S >> +++ b/arch/x86/kernel/head_64.S >> @@ -97,6 +97,7 @@ startup_64: >> * Save the returned mask in %r12 for later use. >> */ >> push %rsi >> + movq %rsi, %rdi >> call sme_enable >> pop %rsi >> movq %rax, %r12 >> diff --git a/arch/x86/kernel/mem_encrypt_init.c b/arch/x86/kernel/mem_encrypt_init.c >> index 07cbb90..35c5e3d 100644 >> --- a/arch/x86/kernel/mem_encrypt_init.c >> +++ b/arch/x86/kernel/mem_encrypt_init.c >> @@ -19,6 +19,12 @@ >> #include <linux/mm.h> >> >> #include <asm/sections.h> >> +#include <asm/processor-flags.h> >> +#include <asm/msr.h> >> +#include <asm/cmdline.h> >> + >> +static char sme_cmdline_arg_on[] __initdata = "mem_encrypt=on"; >> +static char sme_cmdline_arg_off[] __initdata = "mem_encrypt=off"; >> >> extern void sme_encrypt_execute(unsigned long, unsigned long, unsigned long, >> void *, pgd_t *); >> @@ -217,8 +223,71 @@ unsigned long __init sme_get_me_mask(void) >> return sme_me_mask; >> } >> >> -unsigned long __init sme_enable(void) >> +unsigned long __init sme_enable(void *boot_data) > > unsigned long __init sme_enable(struct boot_params *bp) > > works too.
Ok, will do.
> > And then you need to correct the function signature in the > !CONFIG_AMD_MEM_ENCRYPT case, at the end of this file, too: > > unsigned long __init sme_enable(struct boot_params *bp) { return 0; }
Yup, missed that. I'll make it match.
> >> { >> + struct boot_params *bp = boot_data; >> + unsigned int eax, ebx, ecx, edx; >> + unsigned long cmdline_ptr; >> + bool enable_if_found; >> + void *cmdline_arg; >> + u64 msr; >> + >> + /* Check for an AMD processor */ >> + eax = 0; >> + ecx = 0; >> + native_cpuid(&eax, &ebx, &ecx, &edx); >> + if ((ebx != 0x68747541) || (edx != 0x69746e65) || (ecx != 0x444d4163)) >> + goto out; >> + >> + /* Check for the SME support leaf */ >> + eax = 0x80000000; >> + ecx = 0; >> + native_cpuid(&eax, &ebx, &ecx, &edx); >> + if (eax < 0x8000001f) >> + goto out; >> + >> + /* >> + * Check for the SME feature: >> + * CPUID Fn8000_001F[EAX] - Bit 0 >> + * Secure Memory Encryption support >> + * CPUID Fn8000_001F[EBX] - Bits 5:0 >> + * Pagetable bit position used to indicate encryption >> + */ >> + eax = 0x8000001f; >> + ecx = 0; >> + native_cpuid(&eax, &ebx, &ecx, &edx); >> + if (!(eax & 1)) >> + goto out; >> + >> + /* Check if SME is enabled */ >> + msr = native_read_msr(MSR_K8_SYSCFG); > > This native_read_msr() wankery is adding this check: > > if (msr_tracepoint_active(__tracepoint_read_msr)) > > and here it is clearly too early for tracepoints. Please use __rdmsr() > which is purely doing the MSR operation. (... and exception handling for
Ah, good catch. I'll switch to __rdmsr().
> when the RDMSR itself raises an exception but we're very early here too > so the MSR better be there, otherwise we'll blow up).
Yes, it will be there if SME support is indicated in the CPUID result.
> >> + if (!(msr & MSR_K8_SYSCFG_MEM_ENCRYPT)) >> + goto out; >> + >> + /* >> + * Fixups have not been to applied phys_base yet, so we must obtain > > ... not been applied to phys_base yet ...
Yup.
> >> + * the address to the SME command line option in the following way. >> + */ >> + if (IS_ENABLED(CONFIG_AMD_MEM_ENCRYPT_ACTIVE_BY_DEFAULT)) { >> + asm ("lea sme_cmdline_arg_off(%%rip), %0" >> + : "=r" (cmdline_arg) >> + : "p" (sme_cmdline_arg_off)); >> + enable_if_found = false; >> + } else { >> + asm ("lea sme_cmdline_arg_on(%%rip), %0" >> + : "=r" (cmdline_arg) >> + : "p" (sme_cmdline_arg_on)); >> + enable_if_found = true; >> + } >> + >> + cmdline_ptr = bp->hdr.cmd_line_ptr | ((u64)bp->ext_cmd_line_ptr << 32); >> + >> + if (cmdline_find_option_bool((char *)cmdline_ptr, cmdline_arg)) >> + sme_me_mask = enable_if_found ? 1UL << (ebx & 0x3f) : 0; >> + else >> + sme_me_mask = enable_if_found ? 0 : 1UL << (ebx & 0x3f); > > I have a better idea: you can copy __cmdline_find_option() + > cmdline_find_option() to arch/x86/lib/cmdline.c in a pre-patch. Then, > pass in a buffer and check for "on" and "off". This way you don't > have to misuse the _bool() variant for something which is actually > "option=argument".
I can do that. Because phys_base hasn't been updated yet, I'll have to create "on" and "off" constants and get their address in a similar way to the command line option so that I can do the strncmp properly.
Thanks, Tom
> > Thanks. >
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