Re: [PATCH V3 1/5] Swiotlb: Add Swiotlb bounce buffer remap function for HV IVM

[Tom Lendacky <thomas.lendacky@xxxxxxx>]

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@xxxxxxxxxxxxx>
> > > >
> > > > 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@xxxxxxxxxxxxx>
> > > 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.