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Message-ID: <174617666081.22196.7546626489676308152.tip-bot2@tip-bot2>
Date: Fri, 02 May 2025 09:04:20 -0000
From: "tip-bot2 for Xin Li (Intel)" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "H. Peter Anvin (Intel)" <hpa@...or.com>, "Xin Li (Intel)" <xin@...or.com>,
Ingo Molnar <mingo@...nel.org>, Juergen Gross <jgross@...e.com>,
"Peter Zijlstra (Intel)" <peterz@...radead.org>,
Andy Lutomirski <luto@...nel.org>, Brian Gerst <brgerst@...il.com>,
David Woodhouse <dwmw2@...radead.org>, Josh Poimboeuf <jpoimboe@...hat.com>,
Kees Cook <keescook@...omium.org>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Paolo Bonzini <pbonzini@...hat.com>, Sean Christopherson <seanjc@...gle.com>,
Stefano Stabellini <sstabellini@...nel.org>, Uros Bizjak <ubizjak@...il.com>,
Vitaly Kuznetsov <vkuznets@...hat.com>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: x86/merge] x86/xen/msr: Remove calling
native_{read,write}_msr{,_safe}() in pmu_msr_{read,write}()
The following commit has been merged into the x86/merge branch of tip:
Commit-ID: 0cb6f4128a7d8dca9c9bb45f9ecbddcd5cf377aa
Gitweb: https://git.kernel.org/tip/0cb6f4128a7d8dca9c9bb45f9ecbddcd5cf377aa
Author: Xin Li (Intel) <xin@...or.com>
AuthorDate: Sun, 27 Apr 2025 02:20:22 -07:00
Committer: Ingo Molnar <mingo@...nel.org>
CommitterDate: Fri, 02 May 2025 10:36:35 +02:00
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) <hpa@...or.com>
Signed-off-by: Xin Li (Intel) <xin@...or.com>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Reviewed-by: Juergen Gross <jgross@...e.com>
Acked-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Brian Gerst <brgerst@...il.com>
Cc: David Woodhouse <dwmw2@...radead.org>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Paolo Bonzini <pbonzini@...hat.com>
Cc: Sean Christopherson <seanjc@...gle.com>
Cc: Stefano Stabellini <sstabellini@...nel.org>
Cc: Uros Bizjak <ubizjak@...il.com>
Cc: Vitaly Kuznetsov <vkuznets@...hat.com>
Link: https://lore.kernel.org/r/20250427092027.1598740-11-xin@zytor.com
---
arch/x86/xen/enlighten_pv.c | 8 ++++++--
arch/x86/xen/pmu.c | 27 ++++-----------------------
arch/x86/xen/xen-ops.h | 4 ++--
3 files changed, 12 insertions(+), 27 deletions(-)
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 8ddd9e5..530b59b 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 3c01fba..0062dbb 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 dc886c3..2de3061 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);
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