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Message-ID: <20231013215410.3os6d2ya7v5yu7vd@box.shutemov.name>
Date: Sat, 14 Oct 2023 00:54:10 +0300
From: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: Michael Roth <michael.roth@....com>,
Borislav Petkov <bp@...en8.de>,
Andy Lutomirski <luto@...nel.org>,
Dave Hansen <dave.hansen@...el.com>,
Sean Christopherson <seanjc@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Joerg Roedel <jroedel@...e.de>,
Ard Biesheuvel <ardb@...nel.org>,
Andi Kleen <ak@...ux.intel.com>,
Kuppuswamy Sathyanarayanan
<sathyanarayanan.kuppuswamy@...ux.intel.com>,
David Rientjes <rientjes@...gle.com>,
Tom Lendacky <thomas.lendacky@....com>,
Thomas Gleixner <tglx@...utronix.de>,
Peter Zijlstra <peterz@...radead.org>,
Paolo Bonzini <pbonzini@...hat.com>,
Ingo Molnar <mingo@...hat.com>,
Dario Faggioli <dfaggioli@...e.com>,
Mike Rapoport <rppt@...nel.org>,
David Hildenbrand <david@...hat.com>,
Mel Gorman <mgorman@...hsingularity.net>,
marcelo.cerri@...onical.com, tim.gardner@...onical.com,
khalid.elmously@...onical.com, philip.cox@...onical.com,
aarcange@...hat.com, peterx@...hat.com, x86@...nel.org,
linux-mm@...ck.org, linux-coco@...ts.linux.dev,
linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv14 5/9] efi: Add unaccepted memory support
On Fri, Oct 13, 2023 at 08:27:28PM +0300, Kirill A. Shutemov wrote:
> I will test the idea with larger unit_size to see how it behaves.
It indeed uncovered an issue. We need to record ranges on accepting_list
in unit_size granularity. Otherwise, we fail to stop parallel accept
requests to the same unit_size block if they don't overlap on physical
addresses.
Updated patch:
diff --git a/drivers/firmware/efi/unaccepted_memory.c b/drivers/firmware/efi/unaccepted_memory.c
index 853f7dc3c21d..8af0306c8e5c 100644
--- a/drivers/firmware/efi/unaccepted_memory.c
+++ b/drivers/firmware/efi/unaccepted_memory.c
@@ -5,9 +5,17 @@
#include <linux/spinlock.h>
#include <asm/unaccepted_memory.h>
-/* Protects unaccepted memory bitmap */
+/* Protects unaccepted memory bitmap and accepting_list */
static DEFINE_SPINLOCK(unaccepted_memory_lock);
+struct accept_range {
+ struct list_head list;
+ unsigned long start;
+ unsigned long end;
+};
+
+static LIST_HEAD(accepting_list);
+
/*
* accept_memory() -- Consult bitmap and accept the memory if needed.
*
@@ -24,6 +32,7 @@ void accept_memory(phys_addr_t start, phys_addr_t end)
{
struct efi_unaccepted_memory *unaccepted;
unsigned long range_start, range_end;
+ struct accept_range range, *entry;
unsigned long flags;
u64 unit_size;
@@ -78,20 +87,58 @@ void accept_memory(phys_addr_t start, phys_addr_t end)
if (end > unaccepted->size * unit_size * BITS_PER_BYTE)
end = unaccepted->size * unit_size * BITS_PER_BYTE;
- range_start = start / unit_size;
-
+ range.start = start / unit_size;
+ range.end = DIV_ROUND_UP(end, unit_size);
+retry:
spin_lock_irqsave(&unaccepted_memory_lock, flags);
+
+ /*
+ * Check if anybody works on accepting the same range of the memory.
+ *
+ * The check with unit_size granularity. It is crucial to catch all
+ * accept requests to the same unit_size block, even if they don't
+ * overlap on physical address level.
+ */
+ list_for_each_entry(entry, &accepting_list, list) {
+ if (entry->end < range.start)
+ continue;
+ if (entry->start >= range.end)
+ continue;
+
+ /*
+ * Somebody else accepting the range. Or at least part of it.
+ *
+ * Drop the lock and retry until it is complete.
+ */
+ spin_unlock_irqrestore(&unaccepted_memory_lock, flags);
+ cond_resched();
+ goto retry;
+ }
+
+ /*
+ * Register that the range is about to be accepted.
+ * Make sure nobody else will accept it.
+ */
+ list_add(&range.list, &accepting_list);
+
+ range_start = range.start;
for_each_set_bitrange_from(range_start, range_end, unaccepted->bitmap,
- DIV_ROUND_UP(end, unit_size)) {
+ range.end) {
unsigned long phys_start, phys_end;
unsigned long len = range_end - range_start;
phys_start = range_start * unit_size + unaccepted->phys_base;
phys_end = range_end * unit_size + unaccepted->phys_base;
+ spin_unlock_irqrestore(&unaccepted_memory_lock, flags);
+
arch_accept_memory(phys_start, phys_end);
+
+ spin_lock_irqsave(&unaccepted_memory_lock, flags);
bitmap_clear(unaccepted->bitmap, range_start, len);
}
+
+ list_del(&range.list);
spin_unlock_irqrestore(&unaccepted_memory_lock, flags);
}
--
Kiryl Shutsemau / Kirill A. Shutemov
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