From: Xin Li (Intel) Date: Sun, 27 Apr 2025 09:20:22 +0000 (-0700) Subject: x86/xen/msr: Remove calling native_{read,write}_msr{,_safe}() in pmu_msr_{read,write}() X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=0cb6f4128a7d8dca9c9bb45f9ecbddcd5cf377aa;p=users%2Fdwmw2%2Flinux.git x86/xen/msr: Remove calling native_{read,write}_msr{,_safe}() in pmu_msr_{read,write}() hpa found that pmu_msr_write() is actually a completely pointless function: https://lore.kernel.org/lkml/0ec48b84-d158-47c6-b14c-3563fd14bcc4@zytor.com/ all it does is shuffle some arguments, then calls pmu_msr_chk_emulated() and if it returns true AND the emulated flag is clear then does *exactly the same thing* that the calling code would have done if pmu_msr_write() itself had returned true. And pmu_msr_read() does the equivalent stupidity. Remove the calls to native_{read,write}_msr{,_safe}() within pmu_msr_{read,write}(). Instead reuse the existing calling code that decides whether to call native_{read,write}_msr{,_safe}() based on the return value from pmu_msr_{read,write}(). Consequently, eliminate the need to pass an error pointer to pmu_msr_{read,write}(). While at it, refactor pmu_msr_write() to take the MSR value as a u64 argument, replacing the current dual u32 arguments, because the dual u32 arguments were only used to call native_write_msr{,_safe}(), which has now been removed. Suggested-by: H. Peter Anvin (Intel) Signed-off-by: Xin Li (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Juergen Gross Acked-by: Peter Zijlstra (Intel) Cc: Andy Lutomirski Cc: Brian Gerst Cc: David Woodhouse Cc: H. Peter Anvin Cc: Josh Poimboeuf Cc: Kees Cook Cc: Linus Torvalds Cc: Paolo Bonzini Cc: Sean Christopherson Cc: Stefano Stabellini Cc: Uros Bizjak Cc: Vitaly Kuznetsov Link: https://lore.kernel.org/r/20250427092027.1598740-11-xin@zytor.com --- diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c index 8ddd9e535f996..530b59b0589ce 100644 --- a/arch/x86/xen/enlighten_pv.c +++ b/arch/x86/xen/enlighten_pv.c @@ -1091,7 +1091,7 @@ static u64 xen_do_read_msr(unsigned int msr, int *err) { u64 val = 0; /* Avoid uninitialized value for safe variant. */ - if (pmu_msr_read(msr, &val, err)) + if (pmu_msr_read_emulated(msr, &val)) return val; if (err) @@ -1133,6 +1133,8 @@ static void set_seg(unsigned int which, unsigned int low, unsigned int high, static void xen_do_write_msr(unsigned int msr, unsigned int low, unsigned int high, int *err) { + u64 val; + switch (msr) { case MSR_FS_BASE: set_seg(SEGBASE_FS, low, high, err); @@ -1159,7 +1161,9 @@ static void xen_do_write_msr(unsigned int msr, unsigned int low, break; default: - if (!pmu_msr_write(msr, low, high, err)) { + val = (u64)high << 32 | low; + + if (!pmu_msr_write_emulated(msr, val)) { if (err) *err = native_write_msr_safe(msr, low, high); else diff --git a/arch/x86/xen/pmu.c b/arch/x86/xen/pmu.c index 3c01fbab7a2c5..0062dbbd66612 100644 --- a/arch/x86/xen/pmu.c +++ b/arch/x86/xen/pmu.c @@ -314,37 +314,18 @@ static bool pmu_msr_chk_emulated(unsigned int msr, uint64_t *val, bool is_read, return true; } -bool pmu_msr_read(unsigned int msr, uint64_t *val, int *err) +bool pmu_msr_read_emulated(u32 msr, u64 *val) { bool emulated; - if (!pmu_msr_chk_emulated(msr, val, true, &emulated)) - return false; - - if (!emulated) { - *val = err ? native_read_msr_safe(msr, err) - : native_read_msr(msr); - } - - return true; + return pmu_msr_chk_emulated(msr, val, true, &emulated) && emulated; } -bool pmu_msr_write(unsigned int msr, uint32_t low, uint32_t high, int *err) +bool pmu_msr_write_emulated(u32 msr, u64 val) { - uint64_t val = ((uint64_t)high << 32) | low; bool emulated; - if (!pmu_msr_chk_emulated(msr, &val, false, &emulated)) - return false; - - if (!emulated) { - if (err) - *err = native_write_msr_safe(msr, low, high); - else - native_write_msr(msr, low, high); - } - - return true; + return pmu_msr_chk_emulated(msr, &val, false, &emulated) && emulated; } static u64 xen_amd_read_pmc(int counter) diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h index dc886c3cc24de..2de30618aa5e4 100644 --- a/arch/x86/xen/xen-ops.h +++ b/arch/x86/xen/xen-ops.h @@ -271,8 +271,8 @@ void xen_pmu_finish(int cpu); static inline void xen_pmu_init(int cpu) {} static inline void xen_pmu_finish(int cpu) {} #endif -bool pmu_msr_read(unsigned int msr, uint64_t *val, int *err); -bool pmu_msr_write(unsigned int msr, uint32_t low, uint32_t high, int *err); +bool pmu_msr_read_emulated(u32 msr, u64 *val); +bool pmu_msr_write_emulated(u32 msr, u64 val); int pmu_apic_update(uint32_t reg); u64 xen_read_pmc(int counter);