| Message ID | 20230403174406.4180472-7-ltykernel@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | x86/hyperv/sev: Add AMD sev-snp enlightened guest support on hyperv | expand |
From: Tianyu Lan <ltykernel@gmail.com> Sent: Monday, April 3, 2023 10:44 AM > The Subject prefix for this patch is still wrong. I previously commented on this. :-( It should be Drivers: hv: vmbus: > VMBus post msg, synic event and message pages are shared > with hypervisor and so decrypt these pages in the sev-snp guest. > > Signed-off-by: Tianyu Lan <tiala@microsoft.com> > --- > Change since RFC V3: > * Set encrypt page back in the hv_synic_free() > > Change since RFC V2: > * Fix error in the error code path and encrypt > pages correctly when decryption failure happens. > --- > drivers/hv/hv.c | 42 +++++++++++++++++++++++++++++++++++++++++- > 1 file changed, 41 insertions(+), 1 deletion(-) > > diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c > index 008234894d28..e09cea8f2f04 100644 > --- a/drivers/hv/hv.c > +++ b/drivers/hv/hv.c > @@ -20,6 +20,7 @@ > #include <linux/interrupt.h> > #include <clocksource/hyperv_timer.h> > #include <asm/mshyperv.h> > +#include <linux/set_memory.h> > #include "hyperv_vmbus.h" > > /* The one and only */ > @@ -117,7 +118,7 @@ int hv_post_message(union hv_connection_id connection_id, > > int hv_synic_alloc(void) > { > - int cpu; > + int cpu, ret; > struct hv_per_cpu_context *hv_cpu; > > /* > @@ -168,9 +169,39 @@ int hv_synic_alloc(void) > pr_err("Unable to allocate post msg page\n"); > goto err; > } > + > + if (hv_isolation_type_en_snp()) { > + ret = set_memory_decrypted((unsigned long) > + hv_cpu->synic_message_page, 1); > + if (ret) > + goto err; > + > + ret = set_memory_decrypted((unsigned long) > + hv_cpu->synic_event_page, 1); > + if (ret) > + goto err_decrypt_event_page; > + > + ret = set_memory_decrypted((unsigned long) > + hv_cpu->post_msg_page, 1); > + if (ret) > + goto err_decrypt_msg_page; > + > + memset(hv_cpu->synic_message_page, 0, PAGE_SIZE); > + memset(hv_cpu->synic_event_page, 0, PAGE_SIZE); > + memset(hv_cpu->post_msg_page, 0, PAGE_SIZE); > + } > } > > return 0; > + > +err_decrypt_msg_page: > + set_memory_encrypted((unsigned long) > + hv_cpu->synic_event_page, 1); > + > +err_decrypt_event_page: > + set_memory_encrypted((unsigned long) > + hv_cpu->synic_message_page, 1); > + > err: > /* > * Any memory allocations that succeeded will be freed when > @@ -191,6 +222,15 @@ void hv_synic_free(void) > free_page((unsigned long)hv_cpu->synic_event_page); > free_page((unsigned long)hv_cpu->synic_message_page); > free_page((unsigned long)hv_cpu->post_msg_page); > + > + if (hv_isolation_type_en_snp()) { > + set_memory_encrypted((unsigned long) > + hv_cpu->synic_message_page, 1); > + set_memory_encrypted((unsigned long) > + hv_cpu->synic_event_page, 1); > + set_memory_encrypted((unsigned long) > + hv_cpu->post_msg_page, 1); > + } The re-encryption must be done *before* pages are freed! Furthermore, if the re-encryption fails, we should not free the page as it would pollute the free memory pool. The best we can do is leak the memory. See Patch 5 in Dexuan's TDX series, which does the same thing (but still doesn't get it quite right, per my comments). Michael > } > > kfree(hv_context.hv_numa_map); > -- > 2.25.1
On 4/12/2023 10:32 PM, Michael Kelley (LINUX) wrote: >> @@ -191,6 +222,15 @@ void hv_synic_free(void) >> free_page((unsigned long)hv_cpu->synic_event_page); >> free_page((unsigned long)hv_cpu->synic_message_page); >> free_page((unsigned long)hv_cpu->post_msg_page); >> + >> + if (hv_isolation_type_en_snp()) { >> + set_memory_encrypted((unsigned long) >> + hv_cpu->synic_message_page, 1); >> + set_memory_encrypted((unsigned long) >> + hv_cpu->synic_event_page, 1); >> + set_memory_encrypted((unsigned long) >> + hv_cpu->post_msg_page, 1); >> + } > The re-encryption must be done*before* pages are freed! > > Furthermore, if the re-encryption fails, we should not free > the page as it would pollute the free memory pool. The best > we can do is leak the memory. See Patch 5 in Dexuan's > TDX series, which does the same thing (but still doesn't > get it quite right, per my comments). > You are right. The order is wrong. we should figure out a right solution to handle such case.
diff --git a/drivers/hv/hv.c b/drivers/hv/hv.c index 008234894d28..e09cea8f2f04 100644 --- a/drivers/hv/hv.c +++ b/drivers/hv/hv.c @@ -20,6 +20,7 @@ #include <linux/interrupt.h> #include <clocksource/hyperv_timer.h> #include <asm/mshyperv.h> +#include <linux/set_memory.h> #include "hyperv_vmbus.h" /* The one and only */ @@ -117,7 +118,7 @@ int hv_post_message(union hv_connection_id connection_id, int hv_synic_alloc(void) { - int cpu; + int cpu, ret; struct hv_per_cpu_context *hv_cpu; /* @@ -168,9 +169,39 @@ int hv_synic_alloc(void) pr_err("Unable to allocate post msg page\n"); goto err; } + + if (hv_isolation_type_en_snp()) { + ret = set_memory_decrypted((unsigned long) + hv_cpu->synic_message_page, 1); + if (ret) + goto err; + + ret = set_memory_decrypted((unsigned long) + hv_cpu->synic_event_page, 1); + if (ret) + goto err_decrypt_event_page; + + ret = set_memory_decrypted((unsigned long) + hv_cpu->post_msg_page, 1); + if (ret) + goto err_decrypt_msg_page; + + memset(hv_cpu->synic_message_page, 0, PAGE_SIZE); + memset(hv_cpu->synic_event_page, 0, PAGE_SIZE); + memset(hv_cpu->post_msg_page, 0, PAGE_SIZE); + } } return 0; + +err_decrypt_msg_page: + set_memory_encrypted((unsigned long) + hv_cpu->synic_event_page, 1); + +err_decrypt_event_page: + set_memory_encrypted((unsigned long) + hv_cpu->synic_message_page, 1); + err: /* * Any memory allocations that succeeded will be freed when @@ -191,6 +222,15 @@ void hv_synic_free(void) free_page((unsigned long)hv_cpu->synic_event_page); free_page((unsigned long)hv_cpu->synic_message_page); free_page((unsigned long)hv_cpu->post_msg_page); + + if (hv_isolation_type_en_snp()) { + set_memory_encrypted((unsigned long) + hv_cpu->synic_message_page, 1); + set_memory_encrypted((unsigned long) + hv_cpu->synic_event_page, 1); + set_memory_encrypted((unsigned long) + hv_cpu->post_msg_page, 1); + } } kfree(hv_context.hv_numa_map);