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Date: Fri, 24 Mar 2017 18:12:57 +0100
From: Borislav Petkov <bp@...e.de>
To: Brijesh Singh <brijesh.singh@....com>
Cc: simon.guinot@...uanux.org, linux-efi@...r.kernel.org,
kvm@...r.kernel.org, rkrcmar@...hat.com, matt@...eblueprint.co.uk,
linux-pci@...r.kernel.org, linus.walleij@...aro.org,
gary.hook@....com, linux-mm@...ck.org,
paul.gortmaker@...driver.com, hpa@...or.com, cl@...ux.com,
dan.j.williams@...el.com, aarcange@...hat.com,
sfr@...b.auug.org.au, andriy.shevchenko@...ux.intel.com,
herbert@...dor.apana.org.au, bhe@...hat.com, xemul@...allels.com,
joro@...tes.org, x86@...nel.org, peterz@...radead.org,
piotr.luc@...el.com, mingo@...hat.com, msalter@...hat.com,
ross.zwisler@...ux.intel.com, dyoung@...hat.com,
thomas.lendacky@....com, jroedel@...e.de, keescook@...omium.org,
arnd@...db.de, toshi.kani@....com, mathieu.desnoyers@...icios.com,
luto@...nel.org, devel@...uxdriverproject.org, bhelgaas@...gle.com,
tglx@...utronix.de, mchehab@...nel.org, iamjoonsoo.kim@....com,
labbott@...oraproject.org, tony.luck@...el.com,
alexandre.bounine@....com, kuleshovmail@...il.com,
linux-kernel@...r.kernel.org, mcgrof@...nel.org, mst@...hat.com,
linux-crypto@...r.kernel.org, tj@...nel.org, pbonzini@...hat.com,
akpm@...ux-foundation.org, davem@...emloft.net
Subject: Re: [RFC PATCH v2 15/32] x86: Add support for changing memory
encryption attribute in early boot
On Thu, Mar 02, 2017 at 10:15:28AM -0500, Brijesh Singh wrote:
> Some KVM-specific custom MSRs shares the guest physical address with
> hypervisor. When SEV is active, the shared physical address must be mapped
> with encryption attribute cleared so that both hypervsior and guest can
> access the data.
>
> Add APIs to change memory encryption attribute in early boot code.
>
> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
> ---
> arch/x86/include/asm/mem_encrypt.h | 15 +++++++++
> arch/x86/mm/mem_encrypt.c | 63 ++++++++++++++++++++++++++++++++++++
> 2 files changed, 78 insertions(+)
>
> diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h
> index 9799835..95bbe4c 100644
> --- a/arch/x86/include/asm/mem_encrypt.h
> +++ b/arch/x86/include/asm/mem_encrypt.h
> @@ -47,6 +47,9 @@ void __init sme_unmap_bootdata(char *real_mode_data);
>
> void __init sme_early_init(void);
>
> +int __init early_set_memory_decrypted(void *addr, unsigned long size);
> +int __init early_set_memory_encrypted(void *addr, unsigned long size);
> +
> /* Architecture __weak replacement functions */
> void __init mem_encrypt_init(void);
>
> @@ -110,6 +113,18 @@ static inline void __init sme_early_init(void)
> {
> }
>
> +static inline int __init early_set_memory_decrypted(void *addr,
> + unsigned long size)
> +{
> + return 1;
^^^^^^^^
return 1 when !CONFIG_AMD_MEM_ENCRYPT ?
The non-early variants return 0.
> +}
> +
> +static inline int __init early_set_memory_encrypted(void *addr,
> + unsigned long size)
> +{
> + return 1;
> +}
> +
> #define __sme_pa __pa
> #define __sme_pa_nodebug __pa_nodebug
>
> diff --git a/arch/x86/mm/mem_encrypt.c b/arch/x86/mm/mem_encrypt.c
> index 7df5f4c..567e0d8 100644
> --- a/arch/x86/mm/mem_encrypt.c
> +++ b/arch/x86/mm/mem_encrypt.c
> @@ -15,6 +15,7 @@
> #include <linux/mm.h>
> #include <linux/dma-mapping.h>
> #include <linux/swiotlb.h>
> +#include <linux/mem_encrypt.h>
>
> #include <asm/tlbflush.h>
> #include <asm/fixmap.h>
> @@ -258,6 +259,68 @@ static void sme_free(struct device *dev, size_t size, void *vaddr,
> swiotlb_free_coherent(dev, size, vaddr, dma_handle);
> }
>
> +static unsigned long __init get_pte_flags(unsigned long address)
> +{
> + int level;
> + pte_t *pte;
> + unsigned long flags = _KERNPG_TABLE_NOENC | _PAGE_ENC;
> +
> + pte = lookup_address(address, &level);
> + if (!pte)
> + return flags;
> +
> + switch (level) {
> + case PG_LEVEL_4K:
> + flags = pte_flags(*pte);
> + break;
> + case PG_LEVEL_2M:
> + flags = pmd_flags(*(pmd_t *)pte);
> + break;
> + case PG_LEVEL_1G:
> + flags = pud_flags(*(pud_t *)pte);
> + break;
> + default:
> + break;
> + }
> +
> + return flags;
> +}
> +
> +int __init early_set_memory_enc_dec(void *vaddr, unsigned long size,
> + unsigned long flags)
> +{
> + unsigned long pfn, npages;
> + unsigned long addr = (unsigned long)vaddr & PAGE_MASK;
> +
> + /* We are going to change the physical page attribute from C=1 to C=0.
> + * Flush the caches to ensure that all the data with C=1 is flushed to
> + * memory. Any caching of the vaddr after function returns will
> + * use C=0.
> + */
Kernel comments style is:
/*
* A sentence ending with a full-stop.
* Another sentence. ...
* More sentences. ...
*/
> + clflush_cache_range(vaddr, size);
> +
> + npages = PAGE_ALIGN(size) >> PAGE_SHIFT;
> + pfn = slow_virt_to_phys((void *)addr) >> PAGE_SHIFT;
> +
> + return kernel_map_pages_in_pgd(init_mm.pgd, pfn, addr, npages,
> + flags & ~sme_me_mask);
> +
> +}
> +
> +int __init early_set_memory_decrypted(void *vaddr, unsigned long size)
> +{
> + unsigned long flags = get_pte_flags((unsigned long)vaddr);
So this does lookup_address()...
> + return early_set_memory_enc_dec(vaddr, size, flags & ~sme_me_mask);
... and this does it too in slow_virt_to_phys(). So you do it twice per
vaddr.
So why don't you define a __slow_virt_to_phys() helper - notice
the "__" - which returns flags in its second parameter and which
slow_virt_to_phys() calls with a NULL second parameter in the other
cases?
--
Regards/Gruss,
Boris.
SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--
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