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Peter Anvin" , Thomas Gleixner , Ingo Molnar , Dave Hansen , Tony Luck , Andy Lutomirski , Rik van Riel , "Ravi V. Shankar" , Sebastian Andrzej Siewior , Fenghua Yu , Peter Zijlstra Subject: Re: [PATCH v2 2/8] x86/fpu/xstate: Separate user and supervisor xfeatures mask Message-ID: <20200221103436.GB25747@zn.tnic> References: <20200121201843.12047-1-yu-cheng.yu@intel.com> <20200121201843.12047-3-yu-cheng.yu@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20200121201843.12047-3-yu-cheng.yu@intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 21, 2020 at 12:18:37PM -0800, Yu-cheng Yu wrote: > diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c > index 400a05e1c1c5..7c7f3efa3c57 100644 > --- a/arch/x86/kernel/fpu/signal.c > +++ b/arch/x86/kernel/fpu/signal.c > @@ -254,11 +254,14 @@ static int copy_user_to_fpregs_zeroing(void __user *buf, u64 xbv, int fx_only) > { > if (use_xsave()) { > if (fx_only) { > - u64 init_bv = xfeatures_mask & ~XFEATURE_MASK_FPSSE; > + u64 init_bv; > + > + init_bv = xfeatures_mask_user() & ~XFEATURE_MASK_FPSSE; > copy_kernel_to_xregs(&init_fpstate.xsave, init_bv); > return copy_user_to_fxregs(buf); > } else { > - u64 init_bv = xfeatures_mask & ~xbv; > + u64 init_bv = xfeatures_mask_user() & ~xbv; > + > if (unlikely(init_bv)) > copy_kernel_to_xregs(&init_fpstate.xsave, init_bv); > return copy_user_to_xregs(buf, xbv); If you don't want to overflow 80 cols here in the fx_only() case, you can do: --- diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c index 7c7f3efa3c57..d7e94677cd31 100644 --- a/arch/x86/kernel/fpu/signal.c +++ b/arch/x86/kernel/fpu/signal.c @@ -252,15 +252,16 @@ sanitize_restored_xstate(union fpregs_state *state, */ static int copy_user_to_fpregs_zeroing(void __user *buf, u64 xbv, int fx_only) { + u64 init_bv; + if (use_xsave()) { if (fx_only) { - u64 init_bv; - init_bv = xfeatures_mask_user() & ~XFEATURE_MASK_FPSSE; + copy_kernel_to_xregs(&init_fpstate.xsave, init_bv); return copy_user_to_fxregs(buf); } else { - u64 init_bv = xfeatures_mask_user() & ~xbv; + init_bv = xfeatures_mask_user() & ~xbv; if (unlikely(init_bv)) copy_kernel_to_xregs(&init_fpstate.xsave, init_bv); ... > @@ -210,19 +211,24 @@ void fpstate_sanitize_xstate(struct fpu *fpu) > */ > void fpu__init_cpu_xstate(void) > { > - if (!boot_cpu_has(X86_FEATURE_XSAVE) || !xfeatures_mask) > + if (!boot_cpu_has(X86_FEATURE_XSAVE) || !xfeatures_mask_all) > return; > /* > * Unsupported supervisor xstates should not be found in > * the xfeatures mask. > */ > - WARN_ONCE((xfeatures_mask & UNSUPPORTED_XFEATURES_MASK_SUPERVISOR), > + WARN_ONCE((xfeatures_mask_all & UNSUPPORTED_XFEATURES_MASK_SUPERVISOR), > "x86/fpu: Found unsupported supervisor xstates.\n"); Let's say which to ease debugging: u64 unsup_bits = xfeatures_mask_all & UNSUPPORTED_XFEATURES_MASK_SUPERVISOR; ... WARN_ONCE(unsup_bits, "x86/fpu: Found unsupported supervisor xstates: 0x%llx\n", unsup_bits); > > - xfeatures_mask &= ~UNSUPPORTED_XFEATURES_MASK_SUPERVISOR; > + xfeatures_mask_all &= ~UNSUPPORTED_XFEATURES_MASK_SUPERVISOR; > > cr4_set_bits(X86_CR4_OSXSAVE); > - xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask); <---- newline here. > + /* > + * XCR_XFEATURE_ENABLED_MASK (aka. XCR0) sets user features > + * managed by XSAVE{C, OPT, S} and XRSTOR{S}. Only XSAVE user > + * states can be set here. > + */ > + xsetbv(XCR_XFEATURE_ENABLED_MASK, xfeatures_mask_user()); > } > > /* > @@ -232,7 +238,7 @@ void fpu__init_cpu_xstate(void) > */ > static int xfeature_enabled(enum xfeature xfeature) static bool > { > - return !!(xfeatures_mask & (1UL << xfeature)); > + return !!(xfeatures_mask_all & (1UL << xfeature)); return xfeatures_mask_all & BIT(xfeature); while at it. > } > > /* > @@ -419,7 +425,7 @@ static void __init setup_init_fpu_buf(void) > > if (boot_cpu_has(X86_FEATURE_XSAVES)) > init_fpstate.xsave.header.xcomp_bv = XCOMP_BV_COMPACTED_FORMAT | > - xfeatures_mask; > + xfeatures_mask_all; > > /* > * Init all the features state with header.xfeatures being 0x0 > @@ -479,7 +485,7 @@ int using_compacted_format(void) > int validate_xstate_header(const struct xstate_header *hdr) > { > /* No unknown or supervisor features may be set */ > - if (hdr->xfeatures & ~(xfeatures_mask & SUPPORTED_XFEATURES_MASK_USER)) > + if (hdr->xfeatures & ~xfeatures_mask_user()) > return -EINVAL; > > /* Userspace must use the uncompacted format */ > @@ -614,7 +620,7 @@ static void do_extra_xstate_size_checks(void) > > > /* > - * Get total size of enabled xstates in XCR0/xfeatures_mask. > + * Get total size of enabled xstates in XCR0 | IA32_XSS. > * > * Note the SDM's wording here. "sub-function 0" only enumerates > * the size of the *user* states. If we use it to size a buffer > @@ -704,7 +710,7 @@ static int __init init_xstate_size(void) > */ > static void fpu__init_disable_system_xstate(void) > { > - xfeatures_mask = 0; > + xfeatures_mask_all = 0; > cr4_clear_bits(X86_CR4_OSXSAVE); > setup_clear_cpu_cap(X86_FEATURE_XSAVE); > } > @@ -739,16 +745,22 @@ void __init fpu__init_system_xstate(void) > return; > } > > + /* > + * Find user xstates supported by the processor. > + */ > cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx); > - xfeatures_mask = eax + ((u64)edx << 32); > + xfeatures_mask_all = eax + ((u64)edx << 32); > + > + /* Place supervisor features in xfeatures_mask_all here */ > Superfluous newline. > - if ((xfeatures_mask & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) { > + if ((xfeatures_mask_user() & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) { > /* > * This indicates that something really unexpected happened > * with the enumeration. Disable XSAVE and try to continue > * booting without it. This is too early to BUG(). > */ > - pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n", xfeatures_mask); > + pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n", > + xfeatures_mask_all); > goto out_disable; > } ... -- Regards/Gruss, Boris. https://people.kernel.org/tglx/notes-about-netiquette