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platform_drv: check quota before allocating buffer

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The platform driver uses a 'Constrained_ram_allocator' to allocate
meta-data on behave of a client. It uses the PD session as
'Ram_allocator' back end that in return is implemented via the
'Expanding_pd_session_client'.

Whenever the PD client itselft comes into resource shortage it will
ask its parent unconditionally. However, depending on the integration,
such a request may be left unanswered.

This commit introduces a check to prevent that situation from
occurring. In case the platform driver notices the resource shortage
it will reflect that back to the client.

Issue #4284.
This commit is contained in:
Josef Söntgen 2021-10-04 18:01:48 +02:00 committed by Norman Feske
parent 05b451c563
commit 27e55dab3e
1 changed files with 13 additions and 0 deletions
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13
repos/os/src/drivers/platform/spec/x86/pci_session_component.h
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@ -822,6 +822,19 @@ class Platform::Session_component : public Rpc_object<Session>
Ram_dataspace_capability alloc_dma_buffer(size_t const size, Cache cache) override
{
/*
* Check available quota beforehand and reflect the state back
* to the client because the 'Expanding_pd_session_client' will
* ask its parent otherwise.
*/
enum { WATERMARK_CAP_QUOTA = 8, };
if (_env.pd().avail_caps().value < WATERMARK_CAP_QUOTA)
throw Out_of_caps();
enum { WATERMARK_RAM_QUOTA = 4096, };
if (_env.pd().avail_ram().value < WATERMARK_RAM_QUOTA)
throw Out_of_ram();
Ram_dataspace_capability ram_cap = _env_ram.alloc(size, cache);
addr_t const dma_addr = Dataspace_client(ram_cap).phys_addr();