Re: [PATCH] x86/cpufeatures: Force disable X86_FEATURE_ENQCMD and remove update_pasid()

Borislav Petkov
2021-06-02T10:14:17Z

On Sat, May 29, 2021 at 11:17:30AM +0200, Thomas Gleixner wrote:
> --- a/arch/x86/include/asm/disabled-features.h
> +++ b/arch/x86/include/asm/disabled-features.h
> @@ -56,11 +56,8 @@
> # define DISABLE_PTI (1 << (X86_FEATURE_PTI & 31))
> #endif
>
> -#ifdef CONFIG_IOMMU_SUPPORT
> -# define DISABLE_ENQCMD 0
> -#else
> -# define DISABLE_ENQCMD (1 << (X86_FEATURE_ENQCMD & 31))
> -#endif
> +/* Force disable because it's broken beyond repair */
> +#define DISABLE_ENQCMD (1 << (X86_FEATURE_ENQCMD & 31))

Yeah, for that to work we need:

---
From: Borislav Petkov <bp@suse.de>
Date: Wed, 2 Jun 2021 12:07:52 +0200
Subject: [PATCH] dmaengine: idxd: Use cpu_feature_enabled()

When testing x86 feature bits, use cpu_feature_enabled() so that
build-disabled features can remain off, regardless of what CPUID says.

Fixes: 8e50d392652f ("dmaengine: idxd: Add shared workqueue support")
Signed-off-by: Borislav Petkov <bp@suse.de>
Cc: <stable@vger.kernel.org>
---
drivers/dma/idxd/init.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/dma/idxd/init.c b/drivers/dma/idxd/init.c
index 2a926bef87f2..776fd44aff5f 100644
--- a/drivers/dma/idxd/init.c
+++ b/drivers/dma/idxd/init.c
@@ -745,12 +745,12 @@ static int __init idxd_init_module(void)
* If the CPU does not support MOVDIR64B or ENQCMDS, there's no point in
* enumerating the device. We can not utilize it.
*/
- if (!boot_cpu_has(X86_FEATURE_MOVDIR64B)) {
+ if (!cpu_feature_enabled(X86_FEATURE_MOVDIR64B)) {
pr_warn("idxd driver failed to load without MOVDIR64B.\n");
return -ENODEV;
}

- if (!boot_cpu_has(X86_FEATURE_ENQCMD))
+ if (!cpu_feature_enabled(X86_FEATURE_ENQCMD))
pr_warn("Platform does not have ENQCMD(S) support.\n");
else
support_enqcmd = true;
--
2.29.2

For the newly CCed parties, pls check

https://lkml.kernel.org/r/87mtsd6gr9.ffs@nanos.tec.linutronix.de

for more info.

Thx.

--
Regards/Gruss,
Boris.