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Date:   Wed, 27 Jul 2022 19:01:34 +0200
From:   Borislav Petkov <bp@alien8.de>
To:     Ashish Kalra <Ashish.Kalra@amd.com>
Cc:     x86@kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
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Subject: Re: [PATCH Part2 v6 07/49] x86/sev: Invalid pages from direct map
 when adding it to RMP table
Message-ID: <YuFvbm/Zck9Tr5pq@zn.tnic>
References: <cover.1655761627.git.ashish.kalra@amd.com>
 <243778c282cd55a554af9c11d2ecd3ff9ea6820f.1655761627.git.ashish.kalra@amd.com>
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On Mon, Jun 20, 2022 at 11:03:07PM +0000, Ashish Kalra wrote:

> Subject: x86/sev: Invalid pages from direct map when adding it to RMP table

"...: Invalidate pages from the direct map when adding them to the RMP table"

> +static int restore_direct_map(u64 pfn, int npages)
> +{
> +	int i, ret = 0;
> +
> +	for (i = 0; i < npages; i++) {
> +		ret = set_direct_map_default_noflush(pfn_to_page(pfn + i));

set_memory_p() ?

> +		if (ret)
> +			goto cleanup;
> +	}
> +
> +cleanup:
> +	WARN(ret > 0, "Failed to restore direct map for pfn 0x%llx\n", pfn + i);

Warn for each pfn?!

That'll flood dmesg mightily.

> +	return ret;
> +}
> +
> +static int invalid_direct_map(unsigned long pfn, int npages)
> +{
> +	int i, ret = 0;
> +
> +	for (i = 0; i < npages; i++) {
> +		ret = set_direct_map_invalid_noflush(pfn_to_page(pfn + i));

As above, set_memory_np() doesn't work here instead of looping over each
page?

> @@ -2462,11 +2494,38 @@ static int rmpupdate(u64 pfn, struct rmpupdate *val)
>  	if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP))
>  		return -ENXIO;
>  
> +	level = RMP_TO_X86_PG_LEVEL(val->pagesize);
> +	npages = page_level_size(level) / PAGE_SIZE;
> +
> +	/*
> +	 * If page is getting assigned in the RMP table then unmap it from the
> +	 * direct map.
> +	 */
> +	if (val->assigned) {
> +		if (invalid_direct_map(pfn, npages)) {
> +			pr_err("Failed to unmap pfn 0x%llx pages %d from direct_map\n",

"Failed to unmap %d pages at pfn 0x... from the direct map\n"

> +			       pfn, npages);
> +			return -EFAULT;
> +		}
> +	}
> +
>  	/* Binutils version 2.36 supports the RMPUPDATE mnemonic. */
>  	asm volatile(".byte 0xF2, 0x0F, 0x01, 0xFE"
>  		     : "=a"(ret)
>  		     : "a"(paddr), "c"((unsigned long)val)
>  		     : "memory", "cc");
> +
> +	/*
> +	 * Restore the direct map after the page is removed from the RMP table.
> +	 */
> +	if (!ret && !val->assigned) {
> +		if (restore_direct_map(pfn, npages)) {
> +			pr_err("Failed to map pfn 0x%llx pages %d in direct_map\n",

"Failed to map %d pages at pfn 0x... into the direct map\n"

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette