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Date: Fri, 3 Dec 2021 14:06:58 -0600
From: Tom Lendacky <thomas.lendacky@....com>
To: Tianyu Lan <ltykernel@...il.com>, kys@...rosoft.com,
haiyangz@...rosoft.com, sthemmin@...rosoft.com, wei.liu@...nel.org,
decui@...rosoft.com, tglx@...utronix.de, mingo@...hat.com,
bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org,
hpa@...or.com, jgross@...e.com, sstabellini@...nel.org,
boris.ostrovsky@...cle.com, joro@...tes.org, will@...nel.org,
davem@...emloft.net, kuba@...nel.org, jejb@...ux.ibm.com,
martin.petersen@...cle.com, arnd@...db.de, hch@...radead.org,
m.szyprowski@...sung.com, robin.murphy@....com,
Tianyu.Lan@...rosoft.com, xen-devel@...ts.xenproject.org,
michael.h.kelley@...rosoft.com
Cc: iommu@...ts.linux-foundation.org, linux-arch@...r.kernel.org,
linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-scsi@...r.kernel.org, netdev@...r.kernel.org,
vkuznets@...hat.com, brijesh.singh@....com, konrad.wilk@...cle.com,
hch@....de, parri.andrea@...il.com, dave.hansen@...el.com
Subject: Re: [PATCH V3 1/5] Swiotlb: Add Swiotlb bounce buffer remap function
for HV IVM
On 12/3/21 1:11 PM, Tom Lendacky wrote:
> On 12/3/21 5:20 AM, Tianyu Lan wrote:
>> On 12/2/2021 10:42 PM, Tom Lendacky wrote:
>>> On 12/1/21 10:02 AM, Tianyu Lan wrote:
>>>> From: Tianyu Lan <Tianyu.Lan@...rosoft.com>
>>>>
>>>> In Isolation VM with AMD SEV, bounce buffer needs to be accessed via
>>>> extra address space which is above shared_gpa_boundary (E.G 39 bit
>>>> address line) reported by Hyper-V CPUID ISOLATION_CONFIG. The access
>>>> physical address will be original physical address + shared_gpa_boundary.
>>>> The shared_gpa_boundary in the AMD SEV SNP spec is called virtual top of
>>>> memory(vTOM). Memory addresses below vTOM are automatically treated as
>>>> private while memory above vTOM is treated as shared.
>>>>
>>>> Expose swiotlb_unencrypted_base for platforms to set unencrypted
>>>> memory base offset and platform calls swiotlb_update_mem_attributes()
>>>> to remap swiotlb mem to unencrypted address space. memremap() can
>>>> not be called in the early stage and so put remapping code into
>>>> swiotlb_update_mem_attributes(). Store remap address and use it to copy
>>>> data from/to swiotlb bounce buffer.
>>>>
>>>> Signed-off-by: Tianyu Lan <Tianyu.Lan@...rosoft.com>
>>>
>>> This patch results in the following stack trace during a bare-metal boot
>>> on my EPYC system with SME active (e.g. mem_encrypt=on):
>>>
>>> [ 0.123932] BUG: Bad page state in process swapper pfn:108001
>>> [ 0.123942] page:(____ptrval____) refcount:0 mapcount:-128
>>> mapping:0000000000000000 index:0x0 pfn:0x108001
>>> [ 0.123946] flags: 0x17ffffc0000000(node=0|zone=2|lastcpupid=0x1fffff)
>>> [ 0.123952] raw: 0017ffffc0000000 ffff88904f2d5e80 ffff88904f2d5e80
>>> 0000000000000000
>>> [ 0.123954] raw: 0000000000000000 0000000000000000 00000000ffffff7f
>>> 0000000000000000
>>> [ 0.123955] page dumped because: nonzero mapcount
>>> [ 0.123957] Modules linked in:
>>> [ 0.123961] CPU: 0 PID: 0 Comm: swapper Not tainted
>>> 5.16.0-rc3-sos-custom #2
>>> [ 0.123964] Hardware name: AMD Corporation
>>> [ 0.123967] Call Trace:
>>> [ 0.123971] <TASK>
>>> [ 0.123975] dump_stack_lvl+0x48/0x5e
>>> [ 0.123985] bad_page.cold+0x65/0x96
>>> [ 0.123990] __free_pages_ok+0x3a8/0x410
>>> [ 0.123996] memblock_free_all+0x171/0x1dc
>>> [ 0.124005] mem_init+0x1f/0x14b
>>> [ 0.124011] start_kernel+0x3b5/0x6a1
>>> [ 0.124016] secondary_startup_64_no_verify+0xb0/0xbb
>>> [ 0.124022] </TASK>
>>>
>>> I see ~40 of these traces, each for different pfns.
>>>
>>> Thanks,
>>> Tom
>>
>> Hi Tom:
>> Thanks for your test. Could you help to test the following patch
>> and check whether it can fix the issue.
>
> The patch is mangled. Is the only difference where set_memory_decrypted()
> is called?
I de-mangled the patch. No more stack traces with SME active.
Thanks,
Tom
>
> Thanks,
> Tom
>
>>
>>
>> diff --git a/include/linux/swiotlb.h b/include/linux/swiotlb.h
>> index 569272871375..f6c3638255d5 100644
>> --- a/include/linux/swiotlb.h
>> +++ b/include/linux/swiotlb.h
>> @@ -73,6 +73,9 @@ extern enum swiotlb_force swiotlb_force;
>> * @end: The end address of the swiotlb memory pool. Used to do
>> a quick
>> * range check to see if the memory was in fact allocated
>> by this
>> * API.
>> + * @vaddr: The vaddr of the swiotlb memory pool. The swiotlb memory
>> pool
>> + * may be remapped in the memory encrypted case and store
>> virtual
>> + * address for bounce buffer operation.
>> * @nslabs: The number of IO TLB blocks (in groups of 64) between
>> @start and
>> * @end. For default swiotlb, this is command line
>> adjustable via
>> * setup_io_tlb_npages.
>> @@ -92,6 +95,7 @@ extern enum swiotlb_force swiotlb_force;
>> struct io_tlb_mem {
>> phys_addr_t start;
>> phys_addr_t end;
>> + void *vaddr;
>> unsigned long nslabs;
>> unsigned long used;
>> unsigned int index;
>> @@ -186,4 +190,6 @@ static inline bool is_swiotlb_for_alloc(struct
>> device *dev)
>> }
>> #endif /* CONFIG_DMA_RESTRICTED_POOL */
>>
>> +extern phys_addr_t swiotlb_unencrypted_base;
>> +
>> #endif /* __LINUX_SWIOTLB_H */
>> diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c
>> index 8e840fbbed7c..34e6ade4f73c 100644
>> --- a/kernel/dma/swiotlb.c
>> +++ b/kernel/dma/swiotlb.c
>> @@ -50,6 +50,7 @@
>> #include <asm/io.h>
>> #include <asm/dma.h>
>>
>> +#include <linux/io.h>
>> #include <linux/init.h>
>> #include <linux/memblock.h>
>> #include <linux/iommu-helper.h>
>> @@ -72,6 +73,8 @@ enum swiotlb_force swiotlb_force;
>>
>> struct io_tlb_mem io_tlb_default_mem;
>>
>> +phys_addr_t swiotlb_unencrypted_base;
>> +
>> /*
>> * Max segment that we can provide which (if pages are contingous) will
>> * not be bounced (unless SWIOTLB_FORCE is set).
>> @@ -155,6 +158,27 @@ static inline unsigned long nr_slots(u64 val)
>> return DIV_ROUND_UP(val, IO_TLB_SIZE);
>> }
>>
>> +/*
>> + * Remap swioltb memory in the unencrypted physical address space
>> + * when swiotlb_unencrypted_base is set. (e.g. for Hyper-V AMD SEV-SNP
>> + * Isolation VMs).
>> + */
>> +void *swiotlb_mem_remap(struct io_tlb_mem *mem, unsigned long bytes)
>> +{
>> + void *vaddr = NULL;
>> +
>> + if (swiotlb_unencrypted_base) {
>> + phys_addr_t paddr = mem->start + swiotlb_unencrypted_base;
>> +
>> + vaddr = memremap(paddr, bytes, MEMREMAP_WB);
>> + if (!vaddr)
>> + pr_err("Failed to map the unencrypted memory
>> %llx size %lx.\n",
>> + paddr, bytes);
>> + }
>> +
>> + return vaddr;
>> +}
>> +
>> /*
>> * Early SWIOTLB allocation may be too early to allow an architecture to
>> * perform the desired operations. This function allows the
>> architecture to
>> @@ -172,7 +196,12 @@ void __init swiotlb_update_mem_attributes(void)
>> vaddr = phys_to_virt(mem->start);
>> bytes = PAGE_ALIGN(mem->nslabs << IO_TLB_SHIFT);
>> set_memory_decrypted((unsigned long)vaddr, bytes >> PAGE_SHIFT);
>> - memset(vaddr, 0, bytes);
>> +
>> + mem->vaddr = swiotlb_mem_remap(mem, bytes);
>> + if (!mem->vaddr)
>> + mem->vaddr = vaddr;
>> +
>> + memset(mem->vaddr, 0, bytes);
>> }
>>
>> static void swiotlb_init_io_tlb_mem(struct io_tlb_mem *mem,
>> phys_addr_t start,
>> @@ -196,7 +225,17 @@ static void swiotlb_init_io_tlb_mem(struct
>> io_tlb_mem *mem, phys_addr_t start,
>> mem->slots[i].orig_addr = INVALID_PHYS_ADDR;
>> mem->slots[i].alloc_size = 0;
>> }
>> +
>> + /*
>> + * If swiotlb_unencrypted_base is set, the bounce buffer memory
>> will
>> + * be remapped and cleared in swiotlb_update_mem_attributes.
>> + */
>> + if (swiotlb_unencrypted_base)
>> + return;
>> +
>> memset(vaddr, 0, bytes);
>> + mem->vaddr = vaddr;
>> + return;
>> }
>>
>> int __init swiotlb_init_with_tbl(char *tlb, unsigned long nslabs, int
>> verbose)
>> @@ -371,7 +410,7 @@ static void swiotlb_bounce(struct device *dev,
>> phys_addr_t tlb_addr, size_t size
>> phys_addr_t orig_addr = mem->slots[index].orig_addr;
>> size_t alloc_size = mem->slots[index].alloc_size;
>> unsigned long pfn = PFN_DOWN(orig_addr);
>> - unsigned char *vaddr = phys_to_virt(tlb_addr);
>> + unsigned char *vaddr = mem->vaddr + tlb_addr - mem->start;
>> unsigned int tlb_offset, orig_addr_offset;
>>
>> if (orig_addr == INVALID_PHYS_ADDR)
>>
>>
>> Thanks.
>>
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