| Message ID | 20221020113619.17204-1-jgross@suse.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | x86/xen: simplify sysenter and syscall setup | expand |
On Thu, Oct 20, 2022 at 01:36:19PM +0200, Juergen Gross wrote: > xen_enable_sysenter() and xen_enable_syscall() can be simplified a lot. > > Signed-off-by: Juergen Gross <jgross@suse.com> > --- > arch/x86/xen/setup.c | 23 ++++++----------------- > 1 file changed, 6 insertions(+), 17 deletions(-) > > diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c > index cfa99e8f054b..0f33ed6d3a7b 100644 > --- a/arch/x86/xen/setup.c > +++ b/arch/x86/xen/setup.c > @@ -910,17 +910,9 @@ static int register_callback(unsigned type, const void *func) > > void xen_enable_sysenter(void) > { > - int ret; > - unsigned sysenter_feature; > - > - sysenter_feature = X86_FEATURE_SYSENTER32; > - > - if (!boot_cpu_has(sysenter_feature)) > - return; > - > - ret = register_callback(CALLBACKTYPE_sysenter, xen_entry_SYSENTER_compat); > - if(ret != 0) > - setup_clear_cpu_cap(sysenter_feature); > + if (boot_cpu_has(X86_FEATURE_SYSENTER32) && Can you switch that and below to cpu_feature_enabled() while at it, pls? > + if (boot_cpu_has(X86_FEATURE_SYSCALL32) && ^^^^^^^^^^^^^^^^^^ Thx.
On 20.10.22 13:39, Borislav Petkov wrote: > On Thu, Oct 20, 2022 at 01:36:19PM +0200, Juergen Gross wrote: >> xen_enable_sysenter() and xen_enable_syscall() can be simplified a lot. >> >> Signed-off-by: Juergen Gross <jgross@suse.com> >> --- >> arch/x86/xen/setup.c | 23 ++++++----------------- >> 1 file changed, 6 insertions(+), 17 deletions(-) >> >> diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c >> index cfa99e8f054b..0f33ed6d3a7b 100644 >> --- a/arch/x86/xen/setup.c >> +++ b/arch/x86/xen/setup.c >> @@ -910,17 +910,9 @@ static int register_callback(unsigned type, const void *func) >> >> void xen_enable_sysenter(void) >> { >> - int ret; >> - unsigned sysenter_feature; >> - >> - sysenter_feature = X86_FEATURE_SYSENTER32; >> - >> - if (!boot_cpu_has(sysenter_feature)) >> - return; >> - >> - ret = register_callback(CALLBACKTYPE_sysenter, xen_entry_SYSENTER_compat); >> - if(ret != 0) >> - setup_clear_cpu_cap(sysenter_feature); >> + if (boot_cpu_has(X86_FEATURE_SYSENTER32) && > > Can you switch that and below to cpu_feature_enabled() while at it, pls? > >> + if (boot_cpu_has(X86_FEATURE_SYSCALL32) && > ^^^^^^^^^^^^^^^^^^ Yes, of course. Juergen
On 20/10/2022 12:39, Borislav Petkov wrote: > On Thu, Oct 20, 2022 at 01:36:19PM +0200, Juergen Gross wrote: >> xen_enable_sysenter() and xen_enable_syscall() can be simplified a lot. >> >> Signed-off-by: Juergen Gross <jgross@suse.com> >> --- >> arch/x86/xen/setup.c | 23 ++++++----------------- >> 1 file changed, 6 insertions(+), 17 deletions(-) >> >> diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c >> index cfa99e8f054b..0f33ed6d3a7b 100644 >> --- a/arch/x86/xen/setup.c >> +++ b/arch/x86/xen/setup.c >> @@ -910,17 +910,9 @@ static int register_callback(unsigned type, const void *func) >> >> void xen_enable_sysenter(void) >> { >> - int ret; >> - unsigned sysenter_feature; >> - >> - sysenter_feature = X86_FEATURE_SYSENTER32; >> - >> - if (!boot_cpu_has(sysenter_feature)) >> - return; >> - >> - ret = register_callback(CALLBACKTYPE_sysenter, xen_entry_SYSENTER_compat); >> - if(ret != 0) >> - setup_clear_cpu_cap(sysenter_feature); >> + if (boot_cpu_has(X86_FEATURE_SYSENTER32) && > Can you switch that and below to cpu_feature_enabled() while at it, pls? Why? This function (should) be called on the BSP only (because Xen's API lets this be specified when starting APs). Whether it's once, or one per cpu, it doesn't matter. cpu_feature_enabled() puts in an out-of-line thunk (which is what actually gets used), and a patchable code section. Text patching will happen at least once to orphan the out-of-line thunk, probably after the last time it gets used, then then maybe again later to clear the feature. Even if you had several million CPUs, there's no way the overhead of cpu_feature_enabled() is worth it here. ~Andrew
On 21.10.22 10:06, Andrew Cooper wrote: > On 20/10/2022 12:39, Borislav Petkov wrote: >> On Thu, Oct 20, 2022 at 01:36:19PM +0200, Juergen Gross wrote: >>> xen_enable_sysenter() and xen_enable_syscall() can be simplified a lot. >>> >>> Signed-off-by: Juergen Gross <jgross@suse.com> >>> --- >>> arch/x86/xen/setup.c | 23 ++++++----------------- >>> 1 file changed, 6 insertions(+), 17 deletions(-) >>> >>> diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c >>> index cfa99e8f054b..0f33ed6d3a7b 100644 >>> --- a/arch/x86/xen/setup.c >>> +++ b/arch/x86/xen/setup.c >>> @@ -910,17 +910,9 @@ static int register_callback(unsigned type, const void *func) >>> >>> void xen_enable_sysenter(void) >>> { >>> - int ret; >>> - unsigned sysenter_feature; >>> - >>> - sysenter_feature = X86_FEATURE_SYSENTER32; >>> - >>> - if (!boot_cpu_has(sysenter_feature)) >>> - return; >>> - >>> - ret = register_callback(CALLBACKTYPE_sysenter, xen_entry_SYSENTER_compat); >>> - if(ret != 0) >>> - setup_clear_cpu_cap(sysenter_feature); >>> + if (boot_cpu_has(X86_FEATURE_SYSENTER32) && >> Can you switch that and below to cpu_feature_enabled() while at it, pls? > > Why? > > This function (should) be called on the BSP only (because Xen's API lets > this be specified when starting APs). No, this is true for the syscall callback only. the sysenter and the syscall32 callbacks can only be set via Xen tools or on the local cpu by registering. > > Whether it's once, or one per cpu, it doesn't matter. It does. Juergen
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c index cfa99e8f054b..0f33ed6d3a7b 100644 --- a/arch/x86/xen/setup.c +++ b/arch/x86/xen/setup.c @@ -910,17 +910,9 @@ static int register_callback(unsigned type, const void *func) void xen_enable_sysenter(void) { - int ret; - unsigned sysenter_feature; - - sysenter_feature = X86_FEATURE_SYSENTER32; - - if (!boot_cpu_has(sysenter_feature)) - return; - - ret = register_callback(CALLBACKTYPE_sysenter, xen_entry_SYSENTER_compat); - if(ret != 0) - setup_clear_cpu_cap(sysenter_feature); + if (boot_cpu_has(X86_FEATURE_SYSENTER32) && + register_callback(CALLBACKTYPE_sysenter, xen_entry_SYSENTER_compat)) + setup_clear_cpu_cap(X86_FEATURE_SYSENTER32); } void xen_enable_syscall(void) @@ -934,12 +926,9 @@ void xen_enable_syscall(void) mechanism for syscalls. */ } - if (boot_cpu_has(X86_FEATURE_SYSCALL32)) { - ret = register_callback(CALLBACKTYPE_syscall32, - xen_entry_SYSCALL_compat); - if (ret != 0) - setup_clear_cpu_cap(X86_FEATURE_SYSCALL32); - } + if (boot_cpu_has(X86_FEATURE_SYSCALL32) && + register_callback(CALLBACKTYPE_syscall32, xen_entry_SYSCALL_compat)) + setup_clear_cpu_cap(X86_FEATURE_SYSCALL32); } static void __init xen_pvmmu_arch_setup(void)
xen_enable_sysenter() and xen_enable_syscall() can be simplified a lot. Signed-off-by: Juergen Gross <jgross@suse.com> --- arch/x86/xen/setup.c | 23 ++++++----------------- 1 file changed, 6 insertions(+), 17 deletions(-)