On 12/2/2024 5:44 PM, Kevin Loughlin wrote:
On Mon, Dec 2, 2024 at 5:28 PM Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote:
On 03/12/2024 12:59 am, Kevin Loughlin wrote:
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index d4eb9e1d61b8..c040af2d8eff 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -187,6 +187,13 @@ static __always_inline void wbinvd(void)
PVOP_ALT_VCALL0(cpu.wbinvd, "wbinvd", ALT_NOT_XEN);
}
+extern noinstr void pv_native_wbnoinvd(void);
+
+static __always_inline void wbnoinvd(void)
+{
+ PVOP_ALT_VCALL0(cpu.wbnoinvd, "wbnoinvd", ALT_NOT_XEN);
+}
Given this, ...
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index fec381533555..a66b708d8a1e 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -149,6 +154,7 @@ struct paravirt_patch_template pv_ops = {
.cpu.write_cr0 = native_write_cr0,
.cpu.write_cr4 = native_write_cr4,
.cpu.wbinvd = pv_native_wbinvd,
+ .cpu.wbnoinvd = pv_native_wbnoinvd,
.cpu.read_msr = native_read_msr,
.cpu.write_msr = native_write_msr,
.cpu.read_msr_safe = native_read_msr_safe,
this, and ...
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index d6818c6cafda..a5c76a6f8976 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -1162,6 +1162,7 @@ static const typeof(pv_ops) xen_cpu_ops __initconst = {
.write_cr4 = xen_write_cr4,
.wbinvd = pv_native_wbinvd,
+ .wbnoinvd = pv_native_wbnoinvd,
.read_msr = xen_read_msr,
.write_msr = xen_write_msr,
this, what is the point having a paravirt hook which is wired to
native_wbnoinvd() in all cases?
That just seems like overhead for overhead sake.
I'm mirroring what's done for WBINVD here, which was changed to a
paravirt hook in 10a099405fdf ("cpuidle, xenpv: Make more PARAVIRT_XXL
noinstr clean") in order to avoid calls out to instrumented code as
described in the commit message in more detail. I believe a hook is
similarly required for WBNOINVD, but please let me know if you
disagree. Thanks!
Then the question is why we need to add WBINVD/WBNOINVD to the paravirt
hooks.
